MILWAUKEE (AAAAI) - Genetics play a significant role in peanut allergy say a group of researchers in the July Journal of Allergy and Clinical Immunology, the peer-reviewed, scientific journal of the American Academy of Allergy, Asthma and Immunology (AAAAI).

Lead researcher Scott Sicherer, M.D. and colleagues from Virginia and Belgium performed a twin study to determine if genetic factors influence peanut allergy by comparing the incidence of peanut allergy among identical and fraternal twins. Twin studies are often used to provide information on the relative contribution of genetic factors to a disease when compared with environmental factors.

Previous twin studies have shown high rates of heritability of allergic diseases including asthma, atopic dermatitis and allergic rhinitis. Studies about the genetics of peanut allergy have been limited to a British study that compared the incidence of peanut allergy among siblings with the incidence in the general population. Although the British study showed that peanut allergy had a genetic component, environmental factors may have biased the results.

Fifty-eight pairs of twins (14 identical and 44 fraternal) were recruited for this study with at least one member of each pair having a convincing history of peanut allergy. Seventy individuals had a history of peanut allergy. In 64% of the identical twin pairs, both twins were allergic to peanuts, whereas in the fraternal twin pairs, both twins had peanut allergy 7% of the time. Using this data and a model that considered genetic and environmental factors, researchers calculated a heritability rate of 82% to 87% for peanut allergy. When genetic factors were not considered, the rate dropped to 18.99%, reflecting the importance of the genetic component of peanut allergy. The authors say further studies are needed to closely examine the role of genetices in allergies caused by peanuts and other foods.

It is estimated that up to 8% of children and 2% of adults in the United States are affected by food allergy. Peanuts are one of the most common foods that trigger an allergic reaction, with about three million Americans at risk for reacting to peanuts. An allergic reaction occurs when the immune system overreacts to an ordinarily harmless food. Common symptoms of food allergy can include hives, eczema, asthma and gastrointestinal symptoms such as vomiting, diarrhea and abdominal cramping. The most severe reaction is anaphylaxis, a systemic reaction that can sometimes be fatal.