Discovering the genetic connection through peanut studies on twins

Studies of peanut allergy in twins have provided the strongest proof that genes play a role in developing food allergy but are not exclusively responsible. An important study shows that an identical twin has a 64 percent chance of sharing a peanut allergy with the twin sibling who is allergic to peanut. With nonidentical twins the risk drops to a mere 7 percent.
The study clearly demonstrates a strong genetic link to peanut allergy but also proves that food allergy is not purely a genetic disease. What leads one of the identical twins to develop the allergy and spares the second is unknown. Allergy specialists believe that exposure plays a role in developing a food allergy, but determining exactly what each twin is exposed to in the uncontrolled testing environment of daily living is nearly impossible.