Peanut Allergy
Part One

by Mark Wenger MD, MSc
Allergy and Asthma Associates of Fredericksburg

Peanut allergy accounts for the majority of severe food-related allergic reactions. It usually appears early in life, is often not outgrown, and in some patients a very tiny amount can induce an allergic reaction (one peanut has 200mg of protein, and in the highly allergic, a reaction can occur at less than 5mg, or 1/40th of a peanut!) Research has shown that peanut allergy affects around 1% of the population, or close to three million Americans. The prevalence of peanut allergy doubled from 1997 to 2002. Researchers are not sure what has caused this increase, but the rise in peanut allergy has occurred along with a rise in nearly all allergic diseases. There is thought that this may in part be because our very clean "Western" lifestyle doesn't challenge our immune systems the right way at the right time; instead our immune systems view allergic proteins as the enemy. It also may have to do with the roasting of peanuts - a process that increases the allergenicity of peanut protein. There is less peanut allergy in other parts of the world where peanuts are boiled instead of roasted.

The major problem with peanut allergy is the severity of the reaction. Some recent research suggests that 80% of people with a peanut allergy had a reaction that caused difficulty in their breathing. Although uncommon, peanut allergy accounts for 80% of fatal or near-fatal food allergy reactions. Subsequent exposure to peanut can result in progressively more severe reactions, which is why it is imperative for patients to carry their epinephrine pens at all times. While peanuts are members of the legume (bean) family, just 5% of patients who are allergic to peanuts are allergic to other beans. Of concern, 25-50% of patients with peanut allergies are also allergic to tree nuts, which is one reason we recommend that all peanut-allergic children avoid ALL NUTS.

Testing for allergy can be done effectively at any age. The evaluation for peanut allergy involves a careful and thoughtful history and an evaluation for the presence of allergic antibody to peanut, called IgE. Because most IgE-mediated reactions occur within 60 minutes after ingestion (but may appear as long as 4 hours after) symptoms occurring later than this are unlikely to be a result of the ingestion. The most sensitive way to test for allergies is with a "scratch" test technique - this is done with a plastic device that scratches the surface of the skin with a liquid containing the allergic protein. Another way to test for IgE is with a blood test which gives us a sense of how allergic a patient is. The level of IgE to peanut is important to follow some individuals can outgrow allergy with time. Testing results should always be correlated to the patient's clinical history - just having a blood test positive to peanut does not necessarily mean an allergy to peanut.

While peanut allergy was once considered lifelong, we now know that up to 20% will actually outgrow the allergy by school age. This is particularly true if a child has no other allergic conditions including other food allergies, eczema or asthma. This is in contrast to many other food allergies for which most patients will eventually outgrow. The only way to clear a patient with a history of peanut allergy is to do a food-challenge test under the supervision of a doctor. This is true even if the skin and blood tests have become negative, since 20% of patients with a history of peanut allergy will still react to peanut! If the dietary challenge to peanut (which involves giving incremental portions of peanut protein every 15 to 20 minutes) goes well, an individual can be cleared to eat peanut and should continue to eat at least a small amount monthly to prevent the return of the allergy.

The triad for the management of peanut allergy is to 1) educate patients and their families on how to recognize products that may contain peanut protein 2) teach patients about the early warning signs of an allergic reaction, and 3) to initiate emergency treatment before seeking medical evaluation. All ingredient labels must be carefully read when purchasing prepackaged foods. Also, people must be very cautious when eating foods at restaurants or other peoples' homes where it is possible for food to get contaminated with peanut protein (example: cooking a meal in a pan that previously cooked peanuts). Furthermore, children must be discouraged from sharing food at schools.

We strongly believe there will eventually be a treatment for peanut allergy that will protect patients from the risk of accidental ingestions. While allergy shots are safe for the treatment of airborne allergies, they are not effective for the treatment of food allergies. The future for the treatment of food allergies is very bright. Several academic centers are working to develop a vaccine that would allow children with allergies to foods, such as peanut, to tolerate accidental ingestions. A recent European trial involved administering drops of hazelnut protein under the tongue until desensitization occurred. The results of the trial were encouraging. Until these new treatments arrive, however, vigilant avoidance and epinephrine remain the cornerstones of management.

Dr. Mark Wenger, Msc, is with Allergy and Asthma Associates of Fredericksburg, at both 511 Park Hill Drive, F'Bg, and 12 PGA Drive in Stafford.
Call (540)371-5660.