Peanut allergy: An allergic reaction to peanuts, the leading cause of anaphylaxis, the most severe and potentially life threatening allergic reaction, and the leading cause of death from food allergy in the US and other Western nations.
The prevalence of peanut allergy is increasing. This increase may be due to the exposure of infants with rashes to products such as skin preparations containing peanut oils, sensitizing the children to peanuts.
Peanuts contain the same major allergenic proteins (called Ara h 1, 2, and 3) as tree nuts such as walnuts, cashews, and pistachios. About a third of persons with peanut allergy therefore have subsequent allergic reactions to tree nuts.
To prevent allergic reactions, one should avoid all nuts and foods containing nuts. This is easier said than done. Food labels should be scrutinized and dishes of unknown origin should be avoided. Despite such precautions, people with peanut allergy average a reaction every 3 to 5 years from inadvertent exposure.
A Medic Alert bracelet is advised. Patients and parents of children with peanut allergy should learn the early signs of an allergic reaction such as hives, tongue swelling, throat tightening, and vomiting. They must also carry appropriate medications, including liquid diphenhydramine (Benadryl) and, most importantly, have self-injectable epinephrine (Adrenaline) on hand at all times. It there is accidental peanut exposure, these medications should be used immediately. Then the patient should go to an emergency room as soon as possible for further treatment and for observation because of the risk of a second delayed (biphasic) reaction.
The patient's IgE (immunoglobulin E) is integral to peanut allergy. IgE binds to mast cells and triggers the production and release of histamine and other molecules that mediate the allergic reaction. Antibodies directed against IgE can prevent IgE from binding to mast cells.
Regular injection of a monoclonal anti-IgE antibody raises the threshold of tolerance in patients with peanut allergy. (Instead of reacting to half a peanut, people had no reactions until they ate on the average 9 peanuts.) Anti-IgE provides some protection against inadvertent exposure to peanuts, an everpresent danger.