MILWAUKEE (AAAAI) -- Allergic reactions to peanut and tree nuts are frequently severe, often occur on the first known exposure, and can become more severe over time according to a study in the July JACI. This information comes from the largest voluntary registry of food allergy, comprising 5,149 individuals with self-reported allergy to peanuts and/or tree nuts.

The registry was established in 1997 to learn more about demographics and reactions of those affected. The registry was created through the use of a structured questionnaire distributed to all members of the Food Allergy and Anaphylaxis Network and to AAAAI member-allergists.

Scott Sicherer, MD, Mount Sinai School of Medicine, and colleagues from the Food Allergy and Anaphylaxis Network, Mount Sinai School of Medicine and the University of Arkansas for Medical Sciences, sought to examine characteristics of peanut and tree nut allergy among the first 5,149 registry participants.

Researchers found: -- Sixty-eight percent of patients were allergic to peanuts, 9% were allergic to tree nuts and 23% were allergic to both peanuts and tree nuts.

-- Many reported other food allergies, including egg (29%), cows milk (22%), soy (11%), wheat (6%), fish (4%) and shellfish (2%).

-- Registrants reported having other allergic diseases. Fifty percent reported having atopic dermatitis, 46% had asthma and 27% had allergic rhinitis (hay fever).

For 74% of registrants, their first allergic reaction to peanuts or tree nuts occurred on their first known exposure. The average age at which the first reaction to peanuts occurred was 14 months and the average age for the first reaction to tree nuts was 36 months. Registrants with asthma were more likely than those without asthma to have severe reactions (33% vs. 21%).

Ingestion was the most common form of exposure (91%), followed by skin contact (8%) and airborne exposure (1%). Seventy-two percent of reactions occurred at home and began an average of three minutes after exposure. In comparison with initial reactions, subsequent reactions due to accidental ingestion were more severe.