Arizona Sun

Heat and Sunlight Allergy in Arizona: Yes, It’s a Thing

Can you be allergic to heat and sunlight, two things that Arizona has in extreme abundance?  Unfortunately, the answer is yes.

Allergy to Heat

Normally, people do not break out in itchy hives when spending time in the sun or when exercising although people with chronic inducible urticaria (CIndU) might.  In CIndU, hives and sometimes swelling occurs with exposure to a specific physical stimulus such as heat, cold, scratching, sunlight and even water.

CIndU caused by heat is also called cholinergic urticaria. People with cholinergic urticaria frequently have itching, redness, and small hives whenever there is an elevation in body temperature such as might occur with exercise, taking a hot bath, or sitting in a sauna. The rash can also be triggered by emotional stress or eating spicy and hot food. The trunk, arms, and legs are most frequently involved and the rash usually lasts from 15 minutes to an hour.

The diagnosis is usually apparent from the history but can be confirmed by an exercise challenge.

Treatment usually begins with non-sedating antihistamines such as Claritin, Allegra, Zyrtec or Xyzal.  Antihistamines alone are frequently beneficial although it may take up to four times the usual dose to get things under control. More resistant cases have been treated with a variety of other medications including Xolair given by injection once a month.

Exercise-induced Anaphylaxis

Exercise-induced anaphylaxis is a more serious form of heat allergy. In this condition patients not only break out in hives but can have difficulty breathing and even lose consciousness from a drop in blood pressure with exercise. In some cases, the severe reaction to exercise only occurs if certain foods, such as wheat or peanut, are eaten before the activity.   A careful exercise challenge can confirm the diagnosis and allergy testing can pinpoint the food allergy component.    All patients with this condition should carry an EpiPen, never exercise alone, and strictly avoid food triggers before exercise.

Allergy to Sunlight

It sounds odd and certainly unfortunate if you live in Arizona, but some people will breakout with hives whenever their skin is in direct contact with sunlight for more than a few minutes. This condition is called solar urticaria.

The hives appear on sun-exposed skin several minutes after exposure to a specific wavelength of light and usually last for less than a day as long as you get out of the sun. Covering up to avoid direct contact with the sun is usually helpful although sunscreen, because it does not block the wavelengths of light causing the problem, is not. Phototesting can not only confirm the diagnosis
of solar urticaria but can identify the specific wavelengths of light causing the problem.

Sensitivity to sunlight can cause several other skin disorders called photodermatitis. These conditions, like solar urticaria, occur on sun exposed skin but typically last longer than 24 hrs.

The only thing worse than being allergic to sunlight and heat while living in Arizona is being allergic to dust –  that is definitely a thing.

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.

Sulfa

Sulfa Antibiotic Allergy: Common and Frequently Misunderstood

Sulfa drugs were the first antibiotics

Sulfa drugs were the first chemicals available to treat bacterial infections in humans.  The proper designation for this class of drugs is sulfonamide but they became knows as “sulfa” antibiotics with their widespread use as powders and pills during WW ll.  Although sulfa antibiotics saved lives, their use decreased significantly after the introduction of penicillin because of frequent adverse reactions and emerging bacterial resistance.

Seven Percent of Patients Taking Sulfa Antibiotics Have Adverse Reactions

Approximately 6-8% of patients who take these drugs have adverse skin reactions ranging from a measles-like rash,  hives and swelling, to severe life-threatening skin blistering conditions such as Stevens-Johnson syndrome and toxic epidermal necrolysis.  In HIV- infected patients, the adverse reaction rate to sulfonamide antibiotics is as high as 25 to 50 percent!

For a number of years, the drugs Bactrim DS and Septra DS (which contain two antibiotics: trimethoprim and sulfamethoxazole) were used to treat ear infections in children.  Sulfamethoxazole is a sulfonamide antibiotic.  If patients developed a rash while taking these drugs, they were told that they were allergic to sulfa and should avoid all sulfa drugs in the future.  These antibiotics were widely prescribed and so the number of adults now reporting a history of sulfa allergy is significant.

Sulfa vs Sulfur vs Sulfite vs Sulfate vs…..

As mentioned, “sulfa” is a colloquial designation for sulfonamide antibiotic, but the prefix “sulf” is found in an enormous number of other medications that may contain sulfur, sulfites or bisulfate including penicillin antibiotics, reflux medications, pain medications, blood pressure medications, and a variety of supplements. For example ferrous sulfate is a common medication used to treat iron deficiency.  The chemical structure for the popular diuretic Lasix (furosemide) contains sulfur.   Neither of these medications cross react with sulfonamide antibiotics.

The use of trimethoprim/sulfamethoxazole to ear infections in children has decreased significantly because of an increase in bacterial resistance to these antibiotics.  However, this and other sulfonamide antibiotics are still frequently used to to treat urinary track infections and skin infections with MRSA.

Medications to avoid if you are allergic to sulfa antibiotics

Patients who have had adverse reactions to sulfonamide antibiotics should avoid all sulfonamide antimicrobials including:

  • Sulfamethoxazole, cotrimoxazole
  • Sulfasalazine
  • Sodium sufacetamide
  • Silver sulfadiazine

Other drugs that should be avoided include:

  • Dapsone
  • Darunavir
  • Fosamprenavir
  • Trimethoprim

Drugs that you do not need to avoid if you are allergic to sulfa

Drug class
Drug or compound
Comments
Sulfonamide non-antimicrobials
Alpha-blocker
Tamsulosin
Cross-reactivity is unlikely between sulfonamide antimicrobials and sulfonamide non-antimicrobials
Antiarrhythmics
Ibutilide, sotalol
Anticonvulsants
Topiramate
Carbonic anhydrase inhibitors
Acetazolamide, methazolamide, dorzolamide, brinzolamide
COX-2 inhibitors
Celecoxib
Diuretics, loop
Furosemide, bumetanide
Sulfonylureas
Glimepiride, glyburide, gliclazide
Diuretics, thiazide
Hydrochlorothiazide, chlorthalidone, indapamide, metolazone, diazoxide
Triptans
Sumatriptan, naratriptan
Other
Sulfur
No sulfonamide moiety and therefore no cross-reactivity
Sulfate (eg, ferrous sulfate, magnesium sulfate)
Sulfites (eg, sodium metabisulfite)

Source:  https://doi.org/10.1016/j.jaip.2019.05.034

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?

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”.

What is Blooming in Phoenix?

If you have been sneezing and your eyes and nose stinging and watering you might be asking: “My allergies are driving me crazy, what in the world is blooming this time of year?”

And like many, to find out you might google it, put in your zip code and come up with something like this from Pollen.com.

Source: Pollen.com

Source: Pollen.com

 

Source: Pollen.com

Source: Pollen.com

Seems pretty clear. Your sneezing and drippy nose is being caused by all the pollinating Ragweed, Chenopods (whatever they are), and Sagebrush in your neighborhood.

Perhaps not.

Notice in the map above that Arizona, Southern California, Utah, and Nevada all have the same pollen forecast.  All those regions are pretty much the same aren’t they?  Just like all of Arizona is the same, right?

Perhaps not.

Anyone who has taken a road trip from Phoenix to Prescott, Payson, or Flagstaff in August can tell you that the scenery, not to mention the temperature, changes dramatically as you drive north.  Gliding along on the 1-17, your car is like a time machine driving into the future. You leave the pizza oven called Phoenix with it’s scorched earth landscape and toxic ozone haze, and in two hours you’ve travelled from summer to blissful fall.  The leaves are changing, the air is clear, cool and crisp, (sweater weather) and wild grass on the hill side is swaying in the breeze (along with the ragweed, BTW ).

If you were to continue driving north, past Flagstaff, you would enter yet another ecosystem, the high desert, home to many plants not found in the low desert of South and Central Arizona or around the San Francisco Peaks.  Sagebrush for example is a huge allergy problem in the high desert surrounding Winslow and Page but has minimal presence in Phoenix. (Texas Sage, a common ornamental landscape bush, is not a member of the Sagebrush family.)

Because of the differences in elevation and temperature, the unique ecosystems of Arizona have different pollinating schedules.  Ragweed and Sagebrush may be wreaking havoc in Winslow at the same time that the poor ragweed around Phoenix is just trying to keep from drying up and blowing away.  So a pollen report showing that Ragweed and Sagebrush is high in Arizona is technically accurate but misses the mark for those living in Phoenix.

Some pollen reports seem to group all of the Southwest into the same region.  A report from a pollen counting station located in San Diego will give results that will look very strange if you happen to live in Ahwatukee, even though they are both part of the “Southwest”.

Not Ahwatukee

Not Ahwatukee

To my knowledge, the location of the pollen counting stations for Pollen.com and the weather sites are not listed on their websites.    One of the best sources for pollen levels is the American Academy of Allergy and Immunology.  AAAAI has a rigorous certification process to insure that sights are providing good information. But there is a problem for the Phoenix area.  Below is a map showing the location of certified pollen counting stations in the west.  Notice something missing?

Source: http://www.aaaai.org/global/nab-pollen-counts/western-region

Source: http://www.aaaai.org/global/nab-pollen-counts/western-region

Getting back to the question: “What is blooming in Phoenix”.   This time of year the answer is: “Not much.”

So if pollen counts in Phoenix are low, what is causing all the sneezing, drippy nose, and red, burning, watery eyes in mid August?

For many, this is the problem:

Screen Shot 2017-08-28 at 3.33.21 PM

Source: airnow.gov Phoenix 8/28/2017

Untitled design (2)

High levels of ground level Ozone, common during the hot summer months in Phoenix,  is a significant cause of respiratory symptoms, particularly for those who have allergies and asthma.

But do not feel left out.  Fall will be coming to the desert soon and along with it the seasonal bloom of grass and weed pollen.  And you won’t need a time machine to find it.

Brian Millhollon, MD

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 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

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.

 

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

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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