The process of frying or boiling can reduce the potential for peanuts to cause an allergic reaction, according to a study published last month in the Journal of Allergy and Clinical Immunology (pp. 107:1077-1081).

The study, which was conducted by scientists from the Mount Sinai School of Medicine in New York, worked from the observation of the lower incidence of peanut allergies in China compared to the US. Led by Dr Kirsten Beyer, the research team sought to discover whether the incidence of allergic reactions could be explained by the methods by which peanuts are prepared in different countries. In China peanuts are generally fried or boiled, while in the US they are commonly roasted.

Beyer and colleagues tested the levels of protein production in peanuts which had been fried, boiled or roasted and then tested those proteins for allergenicity by introducing them to blood serum from people who are known to be allergic to peanuts. The study concluded: "roasting uses higher temperatures that apparently increase the allergenic property of peanut proteins and may help explain the difference in prevalence of peanut allergy observed in the two countries."

All three methods of preparation created a similar amount of proteins, stressed the researchers, but the relative amounts of the main allergen Ara h 1 was higher in the roasted peanuts.

The body's response to the different peanuts was also slightly different. The immune system protein IgE, which stimulates an allergic reaction by binding to allergens, did not work as well against the peanuts proteins where there was a lower incidence of Ara h 1.