Allergy to peanuts and other types of nuts and seeds is the most serious form of food allergy. Peanut allergy is commonly associated with allergy to tree nuts, especially Brazil nuts, almonds, hazelnuts and walnuts. The reason why peanuts and nut derivatives are so allergenic remains unknown, though the rise in prevalence is probably due to increased exposure, because of widespread use of peanuts in food manufacture. Sensitivity is often extreme, with minute amounts of the allergen being capable of triggering a rapid and severe type 1 allergic response.

This causes acute oropharyngeal swelling and systematic circulatory effects which can result in asphyxiation and fatal anaphylaxis. In the UK, about six deaths, usually in young people, occur each year as a result of peanut anaphylaxis and many near-fatal episodes occur. The prevalence of peanut allergy is currently in the region of 1.3%.

It appears to be increasing and the age of onset getting younger. It is increasingly being reported during the first year of life. Nut allergy is less likely to be outgrown than most other childhood allergies with only about 10% of sufferers developing a tolerance to peanuts. It is much more likely to resolve if it appears before the age of 3 years. It is less likely to resolve if it develops in older children or adults, or if other IgE mediated food allergies co-exist.