Some perspective on peanut allergy

Food Allergy News published an informative article in the June-July 2003 issue about peanut allergy, written by Dr. Michael Young of Harvard Medical School. I hope sharing some of his thoughts will simplify dealing with children and adults with peanut allergy.

A commonly held belief is that the odor from peanut products such as peanut butter can cause an allergic reaction and anaphylaxis. Interestingly, when peanut-allergic children were not aware of their airborne exposure to peanut butter, no one developed allergic symptoms or anaphylaxis.

Many parents are concerned that the presence of any peanut products can contaminate the surrounding airborne environment making the entire area and room unsafe for a child with peanut allergy. It is necessary to understand several facts to explain reactions from airborne exposure. First, specific food proteins trigger all allergic reactions. Without contact with the protein, there is no allergic reaction.

Second, food proteins are aerosolized into a vapor by the high heating of cooking such as boiling or frying. Airborne exposure consists of small amounts of food protein that can trigger allergic reactions, usually skin rashes and breathing problems. The typical inhalation reaction will be similar to a cat allergic person entering a room with a cat and developing itchy eyes, sneezing, and runny nose. The chance of a life-threatening anaphylactic reaction from airborne exposure is very small.

Is smelling the odor of a food similar to inhaling food protein? The chemicals in food that cause odors are not proteins. These chemicals stimulate nerve endings in the nose, which the brain senses as odors. Therefore, odors are not capable of causing allergic reactions.

In summary, inhalation of peanut protein can cause allergic reactions but usually not systemic anaphylaxis while odors can cause conditioned physiologic responses.

In a well-vented school cafeteria located away from the kitchen and food preparation area, the main source of peanut protein would be from direct ingestion or skin contact, not airborne contact.

Another concern is that peanut residue found on surfaces can cause anaphylaxis. An excellent double blind placebo controlled study on causal contact with peanut butter published in the Journal of Allergy and Clinical Immunology in July 2003 by Steven J. Simonte, M.D., definitely showed that systemic anaphylaxis does not result from skin contact or smelling peanut butter. These casual contacts have caused skin rashes only. There is no evidence that casual contact and minor exposures from inhalation or skin contact have worsened a peanut allergy. Most serious exposure is through direct ingestion with subsequent symptoms.

Most reasonable action plans include 1) no food sharing, 2) hand washing, and 3) peanut-free zones. These guidelines will prevent most allergic reactions. They will also prevent skin contact causing indirect ingestion or mucosal contact (e.g. kissing, wiping eyes or mouth with a hand contaminated with peanut butter, etc.).

The anxiety that comes from being prepared for the worst-case scenario can be allayed by the knowledge that casual contact probably will not cause anaphylaxis and not worsen the allergy long-term. Further, the likelihood of peanut cross-reacting with other legumes, such as soybean, or fruits with pits is small.

The apparent increase in peanut allergy has occurred along with the apparent increase in allergic diseases in children. This opinion was expressed by Gideon Lack, MD, of the Imperial College, London, in The New England Journal of Medicine (2003; 348:977-985) article on peanut allergy in childhood. The investigators also concluded that the intake of soymilk or soy formula or the presence of an oozing and crusting rash were associated with peanut allergy.

In addition peanut allergy was associated with positive family history of peanut allergy, and exposure to topical preparations containing peanut oil. They found no association with maternal consumption of peanuts during pregnancy, arguing against peanut sensitization in utero. Similarly, breast-feeding did not increase the likelihood of peanut allergy.

I hope this information helps clarify any confusion about appropriate guidelines for schools and daycare facilities with children and adults with peanut allergy. Further information is available at the Food Allergy Network, 10400 Eaton Place, Suite 107, Fairfax, Va. 22030-2208 E-mail: faan@foodallergy.org

Paul A.Shapero, M. D., is an allergist in Bangor.