Update on Whooping Cough

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Maricopa County health officials are continuing to report an alarming increase in cases of whooping cough.  In fact, the number of confirmed cases of whooping cough in 2012  in Maricopa County was more than three times the number in 2011, with 282 confirmed cases by September.

Whooping cough or pertussis, caused by the bacteria Bordetella pertussis, is a very contagious infection that can spread rapidly in a community.  Recent studies have suggested that asthmatics are at even greater risk of contracting the illness.  It can be treated with antibiotics such as azithromycin (Zithromax, Z-pack) although it is most effective when given early in the course of the illness.

Pertussis should be considered in anyone with a cough lasting for more than two weeks.  Diagnosis usually requires a nasal swab and culture and needs to be done before antibiotics are started.

Although the highest attack rate of pertussis occurs in children under one year of age, approximately 60 percent of cases now occur in adults.  For this reason the CDC’s Advisory Committee on Immunization Practices recommends that all adults under the age of 65, including all health care personnel, receive a dose of the pertussis vaccine, Tdap, regardless of the time since their last immunization.

Fall Comes to the Desert

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It’s finally starting to feel like fall.  Nighttime and early morning temperatures have dropped below 90 degrees, the monsoon humidity and risk of monster dust storms is on the decline, kids are back in school, and club sports are in full swing.   We are also seeing early signs of the Arizona fall allergy season.   Unlike the Midwest and the South, where fall can bring some of the worst allergy misery of the year, the fall allergy season in the desert can be hit or miss depending on the amount of monsoon rain during the summer.   This year, things are shaping up to be a real hit.  Higher than normal rain fall has produced a bumper crop of allergenic weeds including Russian Thistle (tumble weed), Careless Weed, and Ragweed.  In many parts of the country, ragweed pollen defines the fall allergy season.  In the Phoenix area, ragweed often plays a minor role in the fall allergy season because it is too hot and dry.  On the other hand, ragweed is a major cause of springtime allergy symptoms, particularly when the valley gets sufficient winter rain. This year may be an exception, and residents of Phoenix who usually have allergy problems during the spring may find themselves suffering as much itching, sneezing, and wheezing this September and October as they usually do in March and April.

Bermuda grass, although pollinating throughout the summer, becomes a more serious allergy problem in the fall as children start practicing and playing on bermuda grass sport fields.  Landscapers and homeowners also begin “scalping” and dethatching there bermuda grass lawns in preparation for planting winter rye grass. Scalping a lawn (mowing the grass very close to ground) sends a cloud of bermuda grass dust high into the dry fall air where it can be carried throughout the neighborhood.

All this increase in atmospheric pollen and particulate production is compounded by the phenomenon of temperature inversion.  In the fall, as the nighttime temperatures begin to drop, a layer of cooler air becomes trapped by a layer of warmer air above. Particulates, including dust and pollen, become trapped in this cool air mass close to the ground,  right at nose and mouth level.

Patients with asthma often have a harder time keeping under control during the fall.  This is not only the result of increased fall pollen and air pollution exposure but also because of the fall cold and flu season.  Viral upper respiratory infections are the number one cause of asthma attacks, particularly in school age children.

Food Allergy Boot Camp

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In sports and other competitive pursuits the saying “whatever does not kill you makes you stronger” seems appropriate and possible even comforting.  To have this applied to the topic of food allergy, particularly in children, seems anything but comforting.   Recent research aimed at understanding the complex problem of food allergy suggests that this principle may not be too far from the truth and underlies a significant paradigm shift in how we approach food allergy prevention.  The result is creating a squeeze felt by families with food allergies as well as the physicians who care for them.

Until recently, the American Academy of Pediatrics recommended that infants who were considered at increased risk of developing food allergy because of their family history should avoid peanuts during the first three years of life,  milk for the first year, egg until age two, and tree nuts and fish until three years of age. Also,  it was suggested that mothers avoid peanuts and other allergenic foods during pregnancy and breast-feeding.

Recently, however, these recommendations were withdrawn by the American Academy of Pediatrics because of a lack of current evidence supporting the assumption that delaying introduction of allergenic food helps to reduce the occurrence of food allergy and other allergic disease.  Also noted was a lack of evidence supporting dietary restrictions during pregnancy and breast feeding.  Even the World Health Organization’s strategy to prevent allergy by recommending exclusive beast-feeding for the first six months of an infants life has come into question.  Although breast feeding until four months of age is still recommended, evidence seems to suggest that prolonging breast feeding beyond 4 months of age may acutely increase the likelihood that a child will develop allergies!

So what options are available to parents and physicians to determine if a child is at risk of a serious food allergy because of a family history or other concerns and how can we prevent or reduce the likelihood of a serious food allergy from developing?

The “dual-allergen exposure hypothesis” is a new theory that may shed light on these questions .  This theory suggests that infants come into contact with small amounts of food through the skin as they explore the environment and as a result of this cutaneous contact, become sensitized.  Sensitization is the process of developing allergic antibodies to something in the environment.  These allergy causing antibodies can be detected on an allergy skin test or blood test.

Sensitization does not always lead to clinical allergy.  Why not?  Because between sensitization and allergy symptoms is a third factor:  tolerance.  Tolerance is our bodies way of reining in the inappropriate allergic response, preventing inflammation that we experience as symptoms.  We want tolerance: it’s natural and very effective, and without it, we would be at risk of reacting to many of the foods that we require for adequate nutrition.

The second part of the dual-allergen exposure hypothesis states that, although sensitization may occur through the skin, tolerance occurs through oral exposure.  In other words, eating the food helps to prevent allergies from developing.  The timing and balance of cutaneous and oral exposure determines whether a child at risk will develop adequate tolerance or else develop harmful adverse reactions because of allergy.

The dual-allergen exposure hypothesis has important implications for the use of allergy blood tests in children.  The use of blood tests to diagnose food allergy in children may in fact be causing more severe allergy problems because parents are frequently told to restrict from the diet foods that show up on a blood test (indicting sensitization but not necessarily allergy) and in the process, push the child from sensitization to true food allergy.

There is always some risk when a child is exposed to a food for the first time (as there is with taking their first step or attending their first day of school), but in spite of the risk of a few bumps along the way, early oral exposure to a food may in the end make the child stronger and less vulnerable to more serious food allergies in the future.

Define Your Terms

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“If you wish to converse with me,” said Voltaire, “define your terms”.

In my practice as an allergy specialist, I find the principle of first defining terms before beginning a discussion with a patient to be key.  Particularly the term “allergy”.   “Allergy” is a very common word, frequently used in general conversation, therefore its definition should be fairly clear.  But this may not always be the case, and subtleties of variance in how we define this term can lead to significant misunderstanding.

From an immunologist’s point of view, a scientific definition of allergy could go something like this:

“Allergy is a  hypersensitivity disorder of the immune system which occurs when a person’s immune system reacts to normally harmless substances in the environment. These reactions are acquired, predictable, and rapid. Allergy is one of four forms of hypersensitivity and is formally called type I (or immediate) hypersensitivity. Allergic reactions are distinctive because of excessive activation of certain white blood cells called mast cells and basophils by a type of antibody called Immunoglobulin E (IgE). This reaction results in an inflammatory response which an range from uncomfortable to dangerous”.

In this definition there are a few key points.  Allergy is reaction to specific substances involving a class of antibodies call IgE,resulting in symptoms.

A more conventional, laymen definition of allergy might look like this:  “An allergy is a reaction of the body to something that you eat, drink, breath or come into contact with that makes you itch, sneeze, wheeze, break out in a rash, get a stomach ache, or swell up”.

There are several medical problems that clearly meet this definition of allergy but in fact, are not allergy at all.  An example of this is lactose intolerance.   This is a problem with mammalian milk (cow, goat, even human) which is caused by the lack of an enzyme which is required to digest milk sugar.    Without this enzyme to turn the big lactose sugar molecule into its much smaller and absorbable bits, drinking milk will cause uncomfortable intestinal bloating, gas, and pain.  Although this a clear reaction to a food, no antibodies are involved,  so it is not an allergy.

Another example is Celiac disease.  In  this rare condition, patients become very ill with abdominal cramping, diarrhea, and even severe weight loss when exposed to even small amounts of gluten in their diet.  This difficult condition is definitely caused by an antibody reaction to a particular food, although the antibody is IgA, not IgE, and is therefore by definition, not an allergy.

Allergy has also been defined in terms of a result on a laboratory test  as well as in terms of symptoms.  For example, if a patient has a laboratory blood test that looks for IgE antibodies to food, any positive result might be viewed as proof of a food allergy.   However,  our definition of  allergy also  requires the presence of symptoms.     When a patient shows evidence of IgE antibodies to a food on an allergy test, we use the term “sensitization”.    A blood test for food allergy may show multiple sensitivities, but unless there is a history of adverse symptoms caused by a particular food, there is no allergy.    This means that you could be “sensitized” to something without being “allergic”, but you cannot be allergic if you are not sensitized.   Essential to the diagnosis of food allergy is the presence of symptoms caused by exposure to a food and laboratory evidence (skin test or blood test) of anti-food IgE antibodies.

Sensitivity, the antibody response on a laboratory test for allergy,  is an important definition to keep in mind when we discuss other tests for food allergy, such as the IgG test.  This test is commonly used in Naturopathic  Medicine, a form of alternative medicine, that places a strong emphasis on the role of diet  and food allergy in health and well being. IgG, like IgE, is a class of antibodies produced by our immune system.  Unlike IgE, IgG’s primary job is to defend against infections such as viruses and bacteria.  When you get a flu shot you are boosting the bodies production of anti-flu virus IgG antibodies.  When the real flu tries to invade and make you sick, the anti-flu IgG antibodies are ready to squash them.    Results of these IgG tests for food allergy frequently return a long list of positive reactions, and patients, upon seeing this list, frequently ask the question, “so what am I supposed to eat if I am allergic to all these foods”.

It does seem strange that our bodies would produce antibodies to a food if there is not a problem of some kind. Why would our immune system react to a food unless it had an issue with it, even if I am not aware of a problem or what that issue is?  Naturopaths use this line of reasoning to suggest that some foods cause “hidden allergy” and can be a source of inflammation.  This inflammation could lead to a variety of chronic conditions such as fatigue, headaches, weight gain, depression, mental fogginess, and many others.  However, this assumption is often a misunderstanding.  Some experts believe that the IgG antibody response occurs to the foods we eat the most and may play a role in the proper development of tolerance.  Tolerance is a good thing. Therefore the IgG food allergy test may simply reflect the foods that we eat most commonly, rather than being harmful.  For this reason, most experts agree that the IgG test for food  allergy is unhelpful and may in fact lead to excessive and dangerous food restriction diets.

Arizona Ash Attack

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A bit of bad news if you live in Tempe, Arizona, particularly if you live in or near Warner Ranch,  and are allergic to Ash pollen.

Arizona Ash is a medium to large deciduous tree, growing to 30-50 ft and found natively in Arizona around the Mogollon Rim at an elevation of 2000-6000 ft.  In contrast to the more common varieties of desert trees, such as Mesquite and Palo Verde, that to some look more like large bushes trimmed to look like a tree, the Arizona Ash provokes memories of the kind of stately shade trees found in the Midwest or Northeast, where many migrants to Arizona grew up.

I have heard that homeowners originally buying into the equestrian homesites in Warner Ranch (between Elliot and Ray Road and east of Ahwatukee) in the 80s were strongly encouraged, if not required, to plant an Arizona Ash tree.  The result is an area filled with mature Ash Trees.  The Ash trees began to pollenate around the first of February, a bit early this year, likely because of the warm, sunny weather. When the wind blows there will beenough Ash pollen in the air to affect the surrounding areas of Tempe, Chandler, and Ahwatukee for several weeks to come.

Arizona Cough

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Cough is one of the most common symptoms prompting patients to see a doctor in the United States with an estimated 30 million trips to the doctor for this problem each year. More than 40% of the patients seen in our allergy and pulmonary practice between November and February complain of cough.

Cough is classified as acute, sub acute or chronic depending on how long the symptom has been present.   Acute cough lasts for less than three weeks and is most commonly the result of an acute respiratory tract infection. Other more serious causes of acute cough include pneumonia and in our clinic in Arizona, coccidiomycosis infection or valley fever.

A cough associated with typical cold symptoms may be called bronchitis, particularly when symptoms last for more than a week. Acute bronchitis is most often caused by a viral infection although other respiratory infections besides viruses, including Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Bordetella pertussis may be involved.  Although most viral infections cause symptoms lasting less than 2-3 weeks, some patients with viral or other upper respiratory tract infections will continue to cough for more than eight weeks after the acute infection.  This persistent cough may be the result of a type of airway injury.  Although the source of the infection is gone, the injury remains and takes time to heal.

Another important cause of acute cough in children in adults is pertussis (whooping cough).  Pertussis is a very contagious disease caused by the bacteria Bordetella pertussis. Before the advent of vaccinations in the 1940s, pertussis was a major cause of severe illness and death among infants and children.  Although cases of pertussis decreased by more than 99% after the introduction of pertussis vaccine, it remains a cause for concern, in part because of the incomplete protection provided by the vaccine and the increasing numbers of children that are never vaccinated.  In fact, pertussis is the only vaccine-preventable disease that is associated with increasing deaths in the United States.  In 2010, more than nine thousand cases of whooping cough were reported in California. At least ten infants died from the infection prompting the health authorities to declare a pertusis epidemic.

Pertusis infection usually begins with symptoms similar to the common cold although after several weeks, frequent and often violent coughing begins. The illness is most severe in infants and young children, particularly in those that have not been immunized. In adults, the only symptoms may be a persistent cough.

In a recent study published in The Journal of Allergy and Clinical Immunology (JACI), the risk of adults and children with asthma developing whooping cough was 1.7 times higher than those without asthma, suggesting that asthma significantly increased risk for whooping cough.

A cough lasting more than 4-6 weeks without a clear history of acute respiratory infection is considered chronic and is most likely the result of one of three conditions: asthma, rhinitis/sinusitis and gastroesophageal reflux disease.

Asthma and rhinitis/sinusitis are frequently the result of allergies and so a history of allergies or a positive allergy evaluation strengthens the likelihood that one of these conditions is behind the cough.

Gastroesophageal reflux disease (GERD) and laryngopharyngeal reflux disease (LPR) are conditions associated with the leakage of stomach contents into the esophagus.  In GERD, stomach acid refluxes into the lower esophagus causing irritation and damage.  Exposed nerves in the esophagus can cause cough as well as pain (heartburn).  In LPR, stomach contents may reach to the top of the esophagus causing direct irritation of the throat and possible sinuses.  The throat and upper airway are lined with cells that produce mucous as well as cells that have hair-like projections or cilia that sweeps the mucous to the back of the throat where it is swallowed.  Acid and protein-destroying enzymes in the refluxed stomach contents inflame and  damage the hair cells, hindering the ability to clear mucous.  The result is pooling of mucous in the back of the throat and recurrent cough to clear it.  It is estimated that 50% of patients with LPR have no other symptom of their condition other than cough and is therefore frequently missed.   GERD and LPR should be suspected if an evaluation for allergies, asthma, and sinus disease is negative and the cough fails to respond to conventional treatment.

Hypoallergenic Dogs and Other Mythological Creatures

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When talking with a patient in our allergy clinic, so often the response to my question,  “Are there any pets in the home”, is “yes, a dog, but it is a hypoallergenic dog”.   I also hear, “My breed of dog does not have fur, it has hair”.  The idea being that, since people are allergic to dog “fur”, having a dog with hair rather than fur avoids the potential problem of dog allergy.

So is there such a thing as a hypoallergenic dog?  Are Poodles and Terriers really less allergenic than Golden Retrievers and Springer Spaniels?   A recent study published in the American Journal of Rhinology & Allergy was conducted to answer this question.

In this study, an Internet search was conducted to identify breeds frequently cited as being hypoallergenic. Dust samples were then collected from homes with a variety of both pure bred and mixed breed dogs.  Researchers have identified Canis familiaris 1 as the allergenic protein (allergen) responsible for dog allergy and the amount of this protein in the dust samples collected from the homes was compared between breeds believed to be hypoallergenic versus the non-hypoallergenic breeds.

Their results?  There was no difference in the amount of allergen shedding by dogs classified as hypoallergenic. The researches concluded that clinicians should advise patients that they cannot rely on breeds deemed to be “hypoallergenic” to in fact deposit less allergenic material throughout the home.

So like the unicorn, the hypoallergenic dog with hair rather than fur is likely a mythological creature, frequently found in word-of-mouth fairy tales and Internet sites, but yet to be found in pet stores.

The Asthma – Tylenol Link

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I have been seeing a number of articles in the news recently reporting a theory that acetaminophen (Tylenol) use in children is linked to the development of asthma.  Proponents of the theory site several lines of evidence.  One is the observation that about 30 years ago parents began to give children with fever acetaminophen in place of Aspirin because of a link between Reye’s syndrome and Aspirin.  This occurred about the same time  that researches began to document a significant increase in asthma cases.  Also, studies have shown that parents of children with a diagnosis of asthma report given their children acetaminophen more frequently.

There are problems with using these observations to conclude that acetaminophen use causes asthma.  Most importantly is the fact that viral respiratory infections, like the rhinovirus that causes the common cold,  are by far the most important triggers of wheezing episodes in children. Many children with wheezing episodes associated with colds go on to develop true asthma but many do not.  In addition, researchers have suggested that certain viral respiratory infections such as the respiratory syncytial virus (RSV) may produce a type of airway injury that leads to the development of asthma.   Since children that have more frequent colds and associated conditions such as ear and sinus infections would be given acetaminophen more often for pain and fever, it is difficult to determine the true link.  In other words, is the observed increase in asthma the result of acetaminophen use or a change in the frequency and types of infections (as well as, perhaps, expectations of parents) that the acetaminophen is used to treat?   Other considerations include the use of antibiotics and vaccinations, declining family size, urbanisation, and pasteurization: all dramatically changed in the past thirty years.

One point is clear however: Reporting a link between Tylenol use and asthma will attract more readers than noting that sick children are more likely to have symptoms.

Children born into a home with pets have lower levels of allergic antibodies

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A study reported in an upcoming issue of The Journal of Allergy and Clinical Immunology (JACI), evaluated  the level of allergic antibodies  from birth to 2 years of age in children born into households that kept a pet cat or dog.

Using the population-based Wayne County Health, Environment Allergy and Asthma Longitudinal Study (WHEALS) birth cohort from southeastern Michigan, they analyzed one to four measurements of total IgE in  1,187 infants collected from birth to 2 years of age. Effects of prenatal dog and cat exposure on the shape and pattern of IgE throughout early life were then assessed.

Overall, children from homes with pets had a total IgE  that was an estimated 28% lower then children from  homes without pets. This protective effect of pet exposure was stronger within children born by caesarean section. It is hoped that future studies to  understand the potentially protective effect of prenatal pet exposure will lead to new treatments.

Parents should be aware that other studies have shown that, once a child has become sensitized (“allergic”) to cat or dog  dander, further exposure to a pet can lead to  more severe allergy and asthma symptoms.

When Healthy Foods and Allergies Collide

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Although food and diet fads come and go, there is general agreement that we should eat more raw fruits and vegetables.  Uncooked fruits and vegetables are the richest source of vitamins, minerals and antioxidants- nutrients often lacking in our over-processed, carbohydrate and fat-loaded, American diets.

For many people with pollen allergy, however, eating fruits and uncooked vegetables is not an option.  When they do, the result is often intolerable itching and irritation of the mouth, palate, and throat, and If they eat too much or too fast, they can develop abdominal pain and symptoms of a full blown allergic reaction.

This condition is called the oral allergy syndrome or pollen-food allergy syndrome and occurs when the antibodies that cause seasonal allergy symptoms, usually directed at grass, tree, or weed pollen, react with similar proteins found in food.   For example, patients with ragweed allergy may have problems with bananas, cucumber, and melons because these contain proteins that are similar to proteins found in ragweed pollen. When these anti-ragweed antibodies in the mouth and throat come into contact with the food, a mild allergic reaction occurs with itching and mild swelling. So eating a banana or piece of cantaloupe ends up making you feel like you just ate a bowl of fresh ragweed leaves.

In the same way, if you are allergic to birch tree pollen you may have problems eating a variety of fruits, vegetables, and nuts including apple, peach, apricot, cherry, plum, pear, almond, hazelnut, carrot, celery, parsley, caraway, fennel, coriander, aniseed, soybean and peanut.  Birch trees are common throughout the northern United States and Europe but are rare in Arizona.  However, allergy to Arizona Sycamore, a tree common to mountain and transition zones of Arizona, has been associated with reactions to apple, hazelnut, lettuce, corn, kiwi, peach, and peanuts, and green beans.  Sensitivity to Mugwort, an allergenic weed also prevalent in the Northern United States and Northern Europe, can cause reactions to carrot, celery, parsley, caraway, fennel, coriander, aniseed, bell pepper, black pepper, garlic, and onion as well as mustard, cauliflower, cabbage, and broccoli.

More important to the Southwest is sagebrush sensitivity, which is associated with reactions to carrot and celery.

An important distinction between the oral allergy syndrome and other types of food allergy is the rare occurrence of more serious allergic symptoms.  This is because the proteins in the fruits and vegetables that cause the oral allergy syndrome are very fragile and easily destroyed by digestive enzymes in the mouth and stomach.   So by the time the food leaves the mouth or stomach, the body no longer recognizes it as an allergen.  Cooking also denatures or destroys the allergenic proteins so that foods that cannot be tolerated when raw can be eaten after cooking.  This works out for banana bread and apple pie but cooked watermelon is just not the same.