Macadamia Nut Ice Cream

Diagnosing Food Allergy: The Food Challenge

Fourteen year old Hanna was at the mall with friends when she discovered she was allergic to macadamia nut.  This fact became clear when she nearly died. She had only taken a few bites of the ice cream with macadamia nut from Cold Stone Creamery.  She had eaten a variety of nuts on numerous occasions without problems, her favorites being almond and hazelnut, but his was her  first time to try this macadamia nut.

By the time paramedics had arrived, she was covered in hives, felt dizzy, had vomited, and could not stand

Immediately her mouth began to burn and after a few minutes her face turned bright red.  She felt itchy all over, her eye lids and lips began to swell and she had a hard time breathing.  By the time paramedics had arrived, she was covered in hives, felt dizzy, had vomited, and could not stand.  The paramedics did not waist anytime:  A syringe filled with epinephrine was jabbed into her upper leg, an IV was started and connected to a larger bag of fluid and she was taken to the nearest hospital.  When she arrived at the emergency room she was feeling better, the hives were clearing and she could breath easier.   She was able to go home after several hours.

Trip to the Allergy Office

She was seen in our office the next week for allergy testing.  A small drop of macadamia nut extract was placed on the skin of her back and gently pricked. After 20 minutes the test was read by measuring the size of any swelling at the test site, the “wheal” as well as any redness or erythema.  The size of the test wheal is compared with a negative (saline) and a positive (histamine) control. A wheal that is 3-4 mm larger than the negative control is a positive test. Hanna’s macadamia test was over 20 mm!

For Hanna, the diagnosis of allergy to macadamia nut is clear.  She has a compelling history of typical allergy symptoms appearing within minutes of exposure and a strongly positive result on allergy skin testing to the allergen in question.  The recommendation is also clear.   No macadamia nuts…EVER. She will also need to carry an EpiPen in case of accidental exposure.  Having it nearby could be life saving.

Now let’s back up a notch.

Let’s suppose Hanna stayed home from the mall that day to study for a test and mom decided to make an appointment with an allergist to talk about Hanna’s itchy eyes and sneezing during the spring.   In this alternate universe, Hanna has never eaten macadamia nut.    During the visit mom mentioned that Hanna complained of itching of the mouth with almonds and hazelnuts when she was a child  but is now eating both nuts fairly regularly without problems.  She would like to check for tree nut allergy though, “just to be sure”.

Allergy testing is completed and the results show strongly positive reactions to spring tree and weed pollen.  Testing to the tree nuts showed an 8 mm reaction to almond, 6 mm reaction to Hazelnut, both moderately positive.  Macadamia nut showed a 20 mm skin test reaction.

What is the diagnosis?  Is Hanna allergic to almond and hazelnut?

To answer this important question, we need to start with how we define “allergy”.  The definition of allergy has two parts:

  1. A history of  symptoms (rash, abdominal pain, breathing difficulty, etc.) on exposure to an allergen
  2. A positive result to the suspected allergen on a skin or blood test for allergy

We like to have both to make a diagnosis of allergy. Even though Hanna’s allergy test is positive to almond and hazelnut, she has eaten both frequently without problems.  By definition therefore, she is not allergic to almond or hazelnut.

“Why are the almond and hazelnut allergy tests positive if  she is not allergic.”

There are a number of possibilities but it is most likely that the positive skin test reaction is the result of cross reaction between proteins in the tree nut and very similar proteins in the tree pollen that she is sensitive too. (To learn more about false positive allergy tests, go here.)

Although Hanna understands this explanation (“sort of”) she is still concerned about eating almond and hazelnut now that she knows that the allergy test was positive.  She asks if there is another test that will prove she is not allergic.

In fact, there is….

The Double Blind, Placebo Controlled Food Challenge

The double blind, placebo controlled food challenge is considered the gold standard for diagnosing food allergy.  In this test two foods are prepared, the test food and a placebo food made to look and taste like the test food.  Neither the patient nor those conducting the test  know which is the true food and which is the placebo until after the test is completed.  The use of the placebo removes the chance that symptoms may be related to the patient (or test giver) having symptoms caused by anxiety.

Because of difficulty associated with developing a suitable placebo for every test food, double blind, placebo controlled food challenges are infrequently done.   In stead, open, graduated challenges of the suspected food have become more popular.

Graduated Food Challenge

In this test, the patient is given a very tiny amount of the suspected food while being closely monitored for any signs of a reaction.  If there are no problems after 15-30 minutes, the dose of the food is increased.  This process is continued until a target dose is achieved or until any objective symptoms suggesting a reaction occur.

Allergy testing is always done prior to a food challenge.  If the allergy test is negative or if the patient has a clear history of having eaten the food without problems,  the chance of passing a food challenge is very high.   A food challenge is not recommended in someone who has a clear history of a severe allergic reaction to a food and has a positive allergy test.  Again, this patient is allergic by definition and a food challenge is not needed.

What about the macadamia nut?

More challenging is the question of conducting a food challenge in a patient who shows a strongly positive result on an allergy test and who has never eaten the food.  This is the case with Hanna and the macadamia nut.   Because she has never eaten macadamia nut, there is insufficient information to make a diagnosis of allergy.  On the other hand, the likelihood that she would fail a food challenge test is high because of the strongly positive skin test result.   In this case, the safest recommendation would be for her to avoid macadamia nut.   Although not perfect, cut off values for the size of skin test reaction likely to result in a failed food challenge have been published.

Delayed introduction of allergenic foods because of allergy testing may cause the problem that well-meaning parents are trying to prevent. 

There is increasing evidence that early introduction of allergenic foods to infants is associated with a decrease in food allergy.  For this reason, the unintended consequence of allergy testing of children to foods they have never eaten in hopes that it will be prevent them from having an allergic reaction, is that parents will be afraid to introduce foods that show positive on the test.  Delayed introduction of allergenic foods because of allergy testing may therefore cause the problem that well-meaning parents were trying to prevent.

Peanut snickers

A New (?) Treatment for Peanut Allergy

New Product to Treat Peanut Allergy

The Allergenic Products Advisory Committee of the Food and Drug Administration (FDA) recently voted to recommend approval of a new treatment for peanut allergy to the FDA.  The treatment was previously referred to as AR101 but it is expected to go by the brand name Palforzia,  If as expected,  the FDA gives the go ahead, it will be the first treatment for food allergy approved by the FDA.

A few important points about Palforzia

  1. It is not a medicine.

Palforzia is a capsule filled with a precise amount of peanut powder.  Thats it.

2. Palforzia is a form of oral immunotherapy

Oral immunotherapy is a process of feeding an allergic individual an increasing amount of the food they are allergic to with the goal of increasing the threshold that triggers a reaction. Immunotherapy for airborne allergens such as pollen, mold, and animal dander has been available by subcutaneous injection (allergy shots) for many years and is an effective treatment for seasonal allergies, allergy to pet dander, asthma, and eczema.  Recently, a sublingual (under the tonge) immunotherapy tablet has been approved by the FDA for the treatment of grass and ragweed pollen allergy.  Unfortunately, the grass tablet does not contain Bermuda grass and so is of limited value in Phoenix and other desert communities in Arizona.  This will be the first oral form of immunotherapy to be approved for the treatment of a food allergy.

3. It is not a cure

By increasing the threshold dose of food required to cause a reaction, it is hoped that treatment with Paforzia will decrease the risk of a  life threatening allergic reaction in the event that peanut is eaten by mistake.   It will not allow peanut allergic patients to enjoy a Snickers bar or PBJ sandwich.  With this treatment,  a child who was at risk of a trip to the hospital if he ate half of a peanut,  may be able to tolerate 3-4 peanuts before a severe reaction occurs.

4. It is for life

Patients must take the peanut capsule every day… forever!

5. There are risks

Patients receiving treatment with Paforzia  frequently have allergic reactions to the peanut powder. These reactions range from a stomach ache to anaphylaxis.   For this reason patients on Paforzia must carry self injectable epinephrine at all times.

Weighing the Risks versus Benefits

The challenge for doctors, patients and parents considering this new treatment will be in evaluating the  benefits versus the risks: Does the benefit of having some protection against a life-threatening reaction to an unexpected exposure to peanut outweigh the risk of frequent allergic reactions with the daily treatment?

dandelion-2338683_1920 2

There is No Such Thing as an Allergy Test

I have been teaching medical students in my office for the past several weeks. These first year University of Arizona students have recently completed a block of studies on the immune system and are spending time in an allergy clinic to learn how memorizing a million obscure names and pathways  applies to the real world of clinical medicine.

Each student spends only half a day with us so there is not much time to impart wisdom. Since this may be their only exposure to the specialty, I have tried to come up with a few important “pearls” for them to take with them.

Here is one of those pearls: “There is no such thing as an allergy test.”

Since we spend a lot of time in our practice testing patients to find out what they are allergic to, this statement is usually greeted by the students with a polite stare as if waiting for the punch line.

First year medical students are understandably a bit nervous when introduced to the real world of doctoring for the first time. They are quite sure of one thing: They do not know very much now and that somehow, over the course of just four years, they will be expected to know practically everything. They are also quite sure that they have no idea how this miracle of knowledge transfer is supposed to happen.

So the students typically smile politely and try not to say anything that would make them look any stupider than they feel. I try to reassure them and suggest that if there ever was a time to ask stupid questions, your first few years of medical school would be it.

The assumption that somehow you should know and that surely everyone but you knows is pervasive but also foolish and can be a serious hindrance to learning. Wisdom begins when we are able to put our pride in our pocket,  acknowledge our ignorance, and ask the stupid question. The other students, contrary to your assumption,  are also quite clueless,  and certain to be relieved when you do.

Back to the point. Why is there no such thing as an allergy test and why is this so important for medical students to learn?

The answer is in the definition of allergy.

Allergy is an adverse condition and symptoms caused by immunologic sensitization and exposure to an allergen.  An allergen, almost always a protein, is the thing (food, animal, pollen, mold, etc) that your immune system decides – arguable by mistake – you need to be defended against.  The resulting production of specific antibodies that react with the allergen is called sensitization.   Without it, you are not allergic.

Sensitization is the part that we learn from an allergy test.

However, having symptoms when exposed to the allergen you are sensitive to is also part of the definition of allergy. Without symptoms, you are not allergic. No matter what the results of an allergy test say.

A diagnosis of allergy cannot be made without a careful  history. In fact, when allergy tests alone are used to make a diagnosis of allergy – which is often the case when patients ask their family doctor to order an allergy test to find out what they are allergic to – the results can be confusing and misleading and even dangerous. In my experience, this is often the case.

Inappropriate diagnosis made on the basis of allergy tests alone have led to unnecessary restriction of foods, elimination of loving pets from the home, disruptive changes at home and at school, and prescriptions for insanely expensive medications such as Epipens.

On their own, blood tests and skin tests for allergy can give falsely positive results as often as 50% of the time. That means that if an allergy test is positive for peanut, and no consideration if given to the patient’s history, there is a 50% chance that the patient is allergic to peanuts and a 50% chance that they are not.

If history is not taken into account to make the diagnosis, an allergy test is about as good as flipping a coin.

Coupled with a thorough and accurate history, however, an allergy test is an essential tool for a making a diagnosis of allergy.

The history – listening! – is the most important skill for a physician to learn. And this is why it is important for medical students to remember: “There is no such thing as an allergy test”.

House Dust Mite

House Dust Mites and Monsoon Season in Phoenix

It is monsoon season in Phoenix and the weather is hot and sticky.   As uncomfortable as it may feel, the outdoor humidity level in Phoenix this time of year rarely exceeds 50% and the indoor humidity levels in the typical Phoenix home, with air conditioning running day and night, may average no more than 30-40%.   These levels are still fairly low when compared with the dripping misery the residents of Houston, Mobile, or Chicago have to endure every summer, but significantly higher than the desiccating 21% average humidity in our winter and spring.

Average Humidity In Phoenix 2016

Humidity levels In Phoenix, AZ  July 2016

Humidity levels Houston, Texas August, 2016

Humidity levels Houston, Tx  August, 2016

Why is this important for people with allergies? Many migrants to Phoenix from more humid lands do say that they feel better  living in the dry, desert climate but most important from an allergy perspective, low humidity means no dust mites.

The House Dust Mite is the poster child for indoor allergies in many parts of the world. downloadInnumerable numbers of these microscopic insects eat, grow, raise families, and poop in the part of the home were we spend most of our time, the bedroom.   They like our beds because it provides a rich source of their favorite food: people dander. House Dust Mites feed on the dead skin scales (dander) than we leave behind while tossing and turning trying to get our 8-10 hours.   After a zillion generations of living, eating, pooping, and dying in our beds, the accumulation of house dust mite related “material” in our mattresses, pillows, and comfy down comforters can be disgustingly rich. And all of this is allergenic.
sleeping girl

House dust mite allergy is a major cause of allergic rhinitis and asthma and significant recourses have been directed at limiting our exposure to dust mite allergens in the home, including pillow and mattress covers, removing stuffed animals from the bedroom, pulling up carpeting and rugs, removing upholstered furniture, taking out venetian blinds, and (Say it ain’t so!) removing ceiling fans, to name a few. However in spite of all these disruptive and potentially expensive undertakings in the fight to control the lowly mite,  the most effective deterrent by far has been to reduce indoor humidity.

Like most living things, House Dust Mites are mostly water and since they cannot go downstairs to get a drink of water when they get thirsty, they need to absorb moisture from the atmosphere. Many studies have shown that indoor humidity levels of around 75% are needed for dust mites to thrive.

Which brings me back to why humidity in Phoenix is an important allergy topic. I recently started monitoring the humidity level in my home with a hydrometer. This device keeps track of the current, low, and maximum humidity levels in the home year round.

 

2017-07-18 09.05.17This is a picture of the hydrometer’s current reading. The indoor humidity has stayed around 30-40% during our most humid time of year with a rare spike to just above 50% during a recent storm.   These humidity levels are too low to support House Dust Mite growth.

Unseen monsters, particularly those as ugly as the House Dust Mite, are frequently blamed for our problems when the real cause is unknown, but when we are experiencing mystery allergy symptoms in the home, unless there is an indoor source of moisture, such as an evaporative cooler  or a 500 gallon indoor aquarium or hot tub, a home may contain a lot of dust but not dust mites. Steroid Devil

What goes into allergy shots 2

What Is In Allergy Shots?

A patient’s father recently asked me an insightful question about allergy immunotherapy. Allergy shots had been recommended for his son to treat his seasonal allergy and asthma symptoms and he wanted to know how we decided what allergens to include in the serum.

In some cases, as I explained, the answer is fairly straightforward. If his son had year round allergy symptoms that worsened when he was home on weekends, a very strong reaction to cat dander on allergy testing, and lived in a home with six cats, desensitizing to cat would definitely be a high priority.

More often, the decision is a little more involved but we start with the  following questions:
1. What is the patient sensitive to on allergy testing? When we read an allergy test, a positive reaction is defined as an increase in wheal size (raised area) of 3 mm or greater compared with a negative control or redness around the test site of 10 mm or greater. Skin test reactions are often much larger, however for an allergen to be considered clinically significant, it only has to reach the minimum size.

2. Is the patient currently exposed to the allergens that show positive on the allergy test?  The answer to this can be a bit tricky. For example, a number of people show positive reactions to House Dust Mite on allergy testing. And yet, most experts agree that House Dust Mite levels in the typical Arizona home are too low to cause significant symptoms. This is because House Dust Mites need an indoor humidity level of at least 50% for most of the year to thrive and the majority of homes in the Phoenix area rarely have indoor humidity levels this high. When there is a question, a simple test is to measure the indoor humidity levels in various rooms in the home with an inexpensive hydrometer. Unless the hydrometer readings are above 50%, we may not need to include Hose Dust Mite in the serum mix. However, if a patient frequently travels to more humid climates (anywhere but the South Western United States) and has increased symptoms on these trips, treatment for House Dust Mite may be recommended.

House Dust Mite

House Dust Mite

Why would you react to an allergen on an allergy test if you are not exposed to it?   There are several possible explanations. Your allergic sensitivities  may have developed when you were living in an area where the allergen is more prevalent. For example, if you lived in New Orleans for a number of yeas before moving to Arizona, you might have a strong sensitivity to House Dust Mite on an allergy test because of the high level of mite exposure on the Gulf Coast, but mites would be an unlikely cause of allergy problems in your new home in the desert. Cross reactivity is another reason that you may show a positive test to an allergen that you  have never been exposed to.   For example, the major allergenic protein in House Dust Mite is also found in a number of other insects and is also present in the muscles of  shellfish. If you are allergic to shellfish, you may show a positive reaction to House Dust Mite on testing, even though you have never lived in an area where dust mites are prevalent.

Cat and dog dander exposure is another issue. Several studies have shown that animal dander in school classrooms and work places may reach levels high enough to cause allergy symptoms in sensitized people, even if they do not have pets. It is also possible to bring enough dander home from school or work on your cloths for levels in your home to reach symptom-causing levels!

You can have pet dander without having a pet

You can have pet dander in your home without having a pet

3. Can the allergen be avoided or eliminated from the environment? If a patient has significant allergy problems caused by an indoor pet and that is the only thing they are allergic too, relocating the pet from the home might be the best solution.   This is certainly true in principle but relocating a family pet from the home is frequently not an option and so management with allergy injections may be the only long term solution.

4.  Is the allergen available for immunotherapy? If you developed allergy problems soon after bringing home a pet llama from your travels to Machu Picchu, appropriate material for desensitization may not be readily available.  Because of cost restraints, the companies that provide the material for making allergy immunotherapy extracts limit choices to items that are frequently used.  Even though Phoenix is the 5th largest city in the US, the percentage of people that are exposed to the unique allergens of the Sonoran Desert is small compared with other regions.  For this reason, some allergens that may be important for those living in our area may not be available. For example, Palo Verde, the state tree of Arizona, is not generally available for allergy immunotherapy. What goes into allergy shots 2

food-1186125_1920

Chickpea Allergy

In the past few years I have discovered two foods that I really enjoy but did not eat growing up.   One is hummus and the other is falafel. In fact, I learned how much I enjoy both foods eating at the Pita Jungle in Ahwatukee. Their falafel sandwich with pita bread and hummus on the side is wonderful!   If you asked me a few years ago what hummus and falafel was made of I would have ( I am ashamed to say) drawn a blank. You of course know that both are made from the chickpea.

Chickpea is one of the earliest known cultivated plants. It is packed with nutrients providing high quality protein, carbohydrates and fiber, and is used in traditional dishes around the world. Because it is high in protein and low in fat, it’s popularity as part of a healthy diet has been increasing in the US over the past 10 years.

I recently learned that chickpea has other traditional uses. In some areas of India, for example, infants are bathed in a lotion made from chickpea flour. In fact, I recently saw a 10 year old girl in our office with a history of severe rash and itching of the skin after she was bathed in chickpea flower lotion as an infant.   Her family has had her avoid anything containing chickpea since that time but was concerned about cross reactivity between the chickpea and other foods.

Chickpea is a legume and therefore closely related to other common legumes used as food such as peanut, soy bean, and green pea. Because of this allergenic cross reactivity, many patients who are allergic to one legume will have a positive allergy test (skin test or blood test) to other legumes although they may be able to eat those foods without any problems.   Usually, people who are truly allergic to a legume (have had symptoms when eating the food) will have a larger reaction on an allergy skin test or a higher value on an allergy blood test, but this is not a reliable way to distinguish who is truly allergic from those who have a positive test because of cross reactivity alone.

As an example, the child who had the severe allergic reaction to chickpea flour as an infant tested positive to green pea, soy, and peanut on her allergy tests although she has been eating these foods all her life without problems.  I explained that the child had an allergic sensitivity to many legumes but was only allergic to Chickpea.  This is not an easy concept to grasp.

On the other hand, someone who grew up in the US with a severe peanut allergy may want to be careful before trying unfamiliar dishes in parts of the world where legumes, such as the Chickpea, are used extensively.

 

baby

Don’t Let Your Babies Have Allergy Testing

This month, the National Institute of Allergy and Infectious Diseases published new guidelines for when peanut should be given to infants. The hope is that fewer children will develop peanut allergy as a result of these new recommendations

Screen Shot 2017-01-20 at 10.54.56 AM

The revision of its guidelines for the introduction of allergenic foods was prompted by the startling results of a study published in 2015 called the LEAP (Learning Early about Peanut Allergy) trial. In this study children between 4 and 11 months of age who were considered to be at high risk for developing allergy to peanut were divided into two groups. One group was given peanut to eat on a regular basis while the other group avoided peanut-containing food.   At 60 months of age both groups underwent a food challenge with peanut.

The peanut food challenge was positive in 13.7 % of the children that avoided peanut but only 1.9% in the group that ate peanuts regularly. In children that had a positive allergy skin test reaction to peanut before the study, the results were even more impressive. There was a 70% reduction in the prevalence of peanut allergy in the group given peanut compared with the peanut avoidance group.  In other words, children who were given peanut-containing foods to eat on a regular basis at a young age were significantly less likely to develop peanut allergy.

Here are the New Guidelines

  1. In children who have severe eczema, egg allergy (defined as a history of an allergic reaction to egg and a positive allergy skin prick or a positive oral egg food challenge result), or both, either a blood test or skin test for peanut should be performed. If the peanut allergy test is positive, the child should be referred to an allergy specialist for evaluation and possible oral food challenge with peanut.
  1. Children who have mild to moderate eczema (not severe) should have peanut-containing foods introduced at around 6 month of age
  1. In children who do not have eczema or history of food allergy, peanut should be introduced in an “age appropriate manner in accordance with family preferences and cultural practices”

Take Home Message

There is strong evidence that early introduction of allergenic foods such as peanut protects children from developing food allergy and delaying introduction of allergenic foods may increase the risk of severe food allergy.

Children who do not have severe eczema or a clear history of egg allergy SHOULD NOT have a blood test for food allergy.  The high rate of false positive results in these tests may delay the introduction of allergenic foods and can therefore cause the problem they are trying to prevent.

Children with a history of severe eczema or egg allergy (or any other food allergy) should be referred to an allergy specialist for further evaluation.

Brian Millhollon, MD

 

 

pecos-sign

Goodbye Pecos Road: Our Lungs Will Miss You

For many years, residents of the shinny new master-planned communities of Mountain Park Ranch, The Foothills, and Club West in Ahwatukee had only one way in or out of their neighborhood, giving it the distinction of being called (not so fondly) the largest cul-de-sac in America. To get to work you had your choice of using either Chandler Blvd or Ray Road, two giant arms of a horse shoe-shaped loop, both with a million cars stopped at a million red lights, all trying to get to the interstate at the same time every morning and back to home and supper at the same time every evening.   This tedious, wearisome daily exercise in commuter angst was the one thing that made many homeowners seriously question the wisdom of moving to Ahwatukee.

Then Pecos Road opened up: Ten miles of four-lane heaven connecting the outer frontier of Ahwatukee to Interstate 10 with only three lights.   Like most residents of The Foothills or Clubwest, Pecos Road was my daily commute. I was greeted with hopeful sunrises over the East Valley each morning and contemplative sunsets over the Estrella Mountains and Gila River Indian Reservation in the evening.

pecos sign3I took up cycling 5 years ago (mid-life crisis or early onset dementia?) and like most of the local lycra-ed community trying their best to out-pedal old age, Pecos Road became my second home; the place for serious training when long intervals were needed or to join friends for group rides and the occasional kamikaze sprint at the roads end. On Pecos you could spread you wings and fly for miles.

In less than a year from now, all that will change and Pecos Road will be no more, replaced by a freeway that will provide a bypass route for an endless line of trucks plodding West or East on Interstate 10.

truck-1499377_1920 2

road-signs-936137_1920

The passing of Pecos Road and the coming of the trucks was on my mind today when I read two articles in the Journal of Allergy, Asthma, and Immunology about the harmful effects of living close to a busy freeway.

The first: Inhalation of diesel exhaust and allergen alters human bronchial epithelium DNA methylation, presents evidence that exposure to diesel particles and common environmental allergens, such as pollen and mold, can alter the DNA of the lung.   This change can produce lasting effects on gene expression, cell function, and health. In other words, exposure to diesel particles can alter your DNA in such a way that you develop allergies or asthma, even if you, or your relatives, never had allergies before.

The number of people with allergies and asthma has increased significantly over the past several decades – a rise that has occurred almost exclusively in industrialized countries.   Since exposure to air pollution is one of the factors that characterizes life in the developed countries, the alteration of our DNA by diesel particles may be one of the mechanisms responsible for the world-wide asthma and allergy epidemic.

The second article, Traffic-related air pollution exposure is associated with allergic sensitization, asthma, and poor lung function in middle age, reports more bad news for communities planted close to major freeways.   Numerous studies have shown exposure to traffic-related air pollution to be associated with respiratory problems in children. This study, however, focused on the effect of air pollution on middle aged adults. The researchers concluded that even relatively low levels of air pollution during middle age is associated with increased risk of allergic sensitization, asthma, and diminished lung function.

The growing body of information documenting the harmful effects of traffic-related air pollution is certainly concerning to residents of any community located close to a major freeway. It doesn’t help that in Ahwatukee, these harmful health effects compound the growing sense of loss that many feel as they watch progress take away an old friend.

Brian Millhollon, MD

 

 

 

when-is-an-allergy-testnot-an-allergy-test-1

When is a Food Allergy Test NOT a Food Allergy Test?

Jason is now 15. He is taking AP calculus at Desert Vista High School, plays La Cross after school, is getting his driver’s permit next week, and plans to go to college and study electrical engineering after graduation. He is smart, tall for his age, and spends a little too much time playing video games.

He is also deathly afraid of peanuts.

He is afraid, in spite of the fact that he has never eaten a peanut. He has never enjoyed a Snickers bar, Reese’s Cup, or Kung Pao Chicken, and has certainly never eaten a peanut butter and jelly sandwich for lunch.

And yet, as long as he can remember, his parents have sternly warned him to stay away from peanuts.   He was not allowed to eat lunch with his friend’s at school because he had to eat at a special “peanut free” table and could not have snacks brought by other parents to baseball practice because they might be “contaminated” with peanut.

His parents have had to buy three sets of Epi Pens each year to keep at school, at home, and at his grandparents home, to be used in case he had a severe allergic reaction after eating peanut by mistake. This year his family spent more than a thousand dollars on the Epi Pens.

All in all, Jason’s life and the life of his family has been complicated by the serious threat of peanut allergy. And yet, Jason is not allergic to peanut.

The problem began when Jason was just turning two. He was spending the day at his grandparent’s house and developed a rash on his cheeks and vomited.   His parents became concerned that he may have had an allergic reaction to something he ate and so took him to his pediatrician who decided to run a food allergy panel just to be sure.

The test came back positive for peanut. The pediatrician suggested that it might be best for Jason to avoid peanuts since if was unclear if he may have eaten something that contained peanut at his grandparent’s house.   His parents read a story about a child with severe peanut allergy who died after being kissed by someone who had eaten a peanut and so requested an Epi Pen to keep on hand. All family members, friends, and teachers, were instructed on the importance of strict peanut avoidance when around Jason and on the use of an Epi Pen.

I saw Jason for first time six months ago.   His parents needed a refill of the Epic Pens and since his pediatrician was no longer practicing, they decided to make an appointment with an allergist.

After talking with Jason and his mother, it was clear that Jason did have allergies. He sneezed frequently, complained of stuffy nose and itchy eyes during the spring and fall, particularly while playing La Cross, and on occasion had wheezing and chest tightness after spending time around a friend’s cat.   Mom was not concerned about these symptoms, lot’s of people had them, but she with very concerned about his severe peanut allergy.

Because of his history, allergy testing to pollen, cat dander, and peanut was completed. The results showed very strong reactivity to grass, tree, and weed pollen as well as to cat dander. The skin test to peanut was also mildly positive.

How do we interpret these results? Most importantly, is Jason allergic to peanut?

To begin we rely on three sources of information to help us make a diagnosis of allergy: the patient’s history, laboratory tests, and a food challenge.

In Jason’s case, the history is not very strong for peanut allergy. In fact, it is not clear if he has ever been exposed to peanut.

What about the positive blood test and skin test for peanut allergy?

Both tests rely on the detection of a specific antibody produced by the body that reacts with peanut. When we find these antibodies, called IgE or immunoglobulin E, we can say that the patient shows sensitization to the food being tested. Both the blood test run when Jason was two and the recent skin test are technically not allergy tests, but tests for sensitization.

This distinction in terminology is important because many people have sensitization to a food (based on skin or blood tests) that they have eaten their entire lives without problems. Since food allergy by definition is adverse symptoms caused by exposure to a food that a patient is sensitized to, then without symptoms, there is no allergy.

If we define a perfect food allergy test as being reactive or positive in 100% of patients who have true allergy to the food and non-reactive or negative in 100% of patients who are tolerant of the food, meaning it is safe for them to eat it, then conventional food allergy testing is not very good. In fact, conventional food allergy testing has an approximately 50% false positive rate: Half of the patents that test positive to a food on these allergy tests are NOT allergic to the food. The test’s ability to rule out allergy is better, by some estimates more than 90%: There is less than a 10% chance that a patient with a negative test to a food will have an allergic reaction if they eat the food.

When we say that conventional allergy tests for peanut allergy have a 50% false positive rate we do not mean the test result is an error or mistake. The test accurately detects allergic or IgE antibodies to peanut. But as was mentioned, the presence of these antibodies does not always cause problems when the patient eats peanut and therefore is considered a falsely positive test for food allergy.

To understanding WHY we can have allergic antibodies to a food that we tolerate it is helpful to understand a few things about proteins. You can find a brief introduction to proteins here.

Peanuts, as well as most other foods, contain multiple proteins. The proteins in peanut are given numbered names beginning with Ara h (from the scientific name for peanut Arachis hypogaea). The peanut proteins Ara h1, Ara h2, Ara h3, Ara h6, Ara h8, and Ara h9 have been detected and allergic IgE antibodies have been found that react with each of these proteins.

Some of these peanut proteins, such as Ara h8, are very similar to proteins found in pollen produced by allergenic plants. In fact, if a patient is allergic to birch tree pollen, the anti-birch tree IgE antibodies they produce are likely to react with the Ara h8 protein in peanut. Patients with allergic antibodies to Ara h8 alone rarely have significant peanut allergy and yet will have a positive skin or blood test to peanut. One study showed that 79% of patients who had allergies to pollen reacted positively to peanut on an allergy test but were tolerant of peanut.

Other studies have shown that patients with high levels of allergic antibodies to the Ara h2 protein in peanut are more likely to have true peanut allergy. These observations have led to the development of component allergy tests were a patients blood can be tested for allergic antibodies to a specific food protein, not just the whole food.

Component testing for peanut allergy does show improved diagnostic accuracy compared with conventional blood tests, although it continues to have a high false positive rate and unfortunately can also be negative in patients who have true peanut allergy.

Component allergy testing for peanut was ordered for Jason and the results showed positive to Ara h8 only suggesting that the positive result on the skin test and earlier blood test occurred because of his strong sensitivity to pollen.

The results were discussed with Jason’s parents who asked if there was any other test that might be used to confirm that he is not allergic to peanut.

In fact, the most reliable and considered to be the gold standard for making a diagnosis of food allergy, is the double-blind, placebo-controlled food challenge. In this test, the patient is given a sample of the test food as well as a sample of a similar, non-allergic food as a placebo. Double blinded means that the doctor and technicians conducting the challenge as well as the patient, do not know which is the real test food and which is the placebo. The test is considered positive if the patient shows obvious signs of a reaction after eating the test food but not after eating the placebo.

There are a number of problems with the double-blind, placebo-controlled food challenge: It is difficult to perform, requiring significant time and recourses; A patient can have a severe allergic reaction to the food and therefore the study must conducted by trained personal in a setting that is capable of handling a severe emergency; and it is not always possible to find a suitable food to serve as a placebo.

Because a food challenge carries the very real risk of a severe allergic reaction it is rarely done if either the history or laboratory tests strongly suggest allergy. Open challenges to a food conducted in the allergist office is considered to be an alternative to a blinded, placebo-controlled challenger if the likelihood of significant allergy is considered to be very low based on history and previous tests.

Because of the weak history for peanut allergy and the results of component allergy testing, a peanut challenge in the office was offered to Jason and his parents.

When the food challenge was discussed with Jason he became very anxious and said that he did not see any reason to do it since he has done well staying away from peanut his whole life. He said he felt sick just thinking about it.

Hopefully, Jason’s fear of peanut allergy will subside with time and education and he will someday be able to enjoy a peanut butter and jelly sandwich or Snickers Bar.  And hopefully, improved testing methods as well as better understanding of food allergy will make such cases of unnecessary fear and anxiety over something to be enjoyed a thing of the past.

Brian Millhollon, MD

 

 

What Went Wrong-

Why Do We Have Allergies 2: What Went Wrong?

We Are Not Alone

If you are looking for a trendy term to impress your friends or co-workers, try microbiome. The microbiome refers to the fascinating world of microorganisms (bacteria, viruses and fungi) that not only fill every nook and cranny of the planet we live on but also every nook and cranny of our own bodies.

By some estimates, we have as many microbes living in our bodies as we do our own cells. (Wouldn’t that be a cool fact to throw out at a dinner party?) For the most part, those microbes living in and on our bodies share a symbiotic relationship with us, meaning they help us and we help them. Supposedly, my dog and I share a symbiotic relationship: I provide him food and shelter and he, well… he hangs around the house looking cute and chewing up my shoes and socks.  (Come to think of it, this may be more indicative of a parasitic relationship.)

Not only do the microorganisms in our body help us digest our food, produce vitamins and help fight off infection, they play an important role in regulating our immune system. From infancy on, these single-celled animals communicate with our immune system and explain the ways of the world to it. It is believed that this early-life education is essential for our immune system to grow up and act appropriately: attacking bad guys – like the measles virus – and not reacting with good things like breakfast or the dander from the sock eating dog.

Of course, the process of this early-life microbial education can involve infection.  And yet, these are usually not life threatening infections, and the end result is a strong, wise and well behaved immune system.What Went Wrong- (1) 2

We No Longer Live in the Garden

Getting back to the question of what went wrong to cause us to have allergies, one of the theories is the hygiene hypothesis which proposes that our immune system is adapted to an environment that – at least for people living in Ahwatukee and most of the westernized world- no longer exists.   At one time in our history, our environment was much more complex and diverse from a microbial point of view with exposure to farm animals and other elements of a farming environment as well as large families with lots of runny-nosed siblings to play with. The hygiene hypothesis was proposed in 1989 when researchers noticed that children who grew up on farms or who came from large families with lots of siblings had fewer allergies.

Untitled design (59)

The explanation? Progress and myriad changes associated with modern life such as a decrease in natural birth deliveries, antibiotic use, lack of breast-feeding, pasteurization, Lysol in every kitchen and bathroom, and antimicrobial everything (hand wipes, mouth wash, soaps, detergents) – not to mention a noticeable lack of cows, chickens, and pigs in the yard -reduce an infant’s exposure to the wise microbe masters that once kept or immune system from going down the path of the dark side.Untitled design (58)

Just as children who grow up in an overly protective, sterile, and restrictive parental environment may have difficulty coping with challenges later in life, our pampered undirected immune system may react inappropriately.

The unintended consequence of our quest to control everything has been the emergence of allergy and other chronic inflammatory diseases.  Who knew?

Now that we are beginning to understand why we develop allergies, the big question is how to fix it.  Allergy immunotherapy or desensitization is essentially a way of re-educating the immune system to behave more appropriately towards our environment.   It is not a quick fix, but the end result can be life-long immunity to things we are allergic to.  New forms of immunotherapy are in the works that combine conventional immunotherapy with elements of the microbiome to mimic the type of early-life training that has been lost (along with paradise).

Brian Millhollon, MD