Peanut and tree nut allergies are types of food allergy. Food allergy occurs when the body’s immune system wrongly identifies a food as a threat. When this happens, the body releases chemicals, such as histamine, in response to exposure to the food. It is the release of these chemicals that causes the allergic symptoms
The peanut is a legume and is in the same plant family as peas, beans and lentils. Tree nuts are in different plant families and include almonds, hazelnuts, walnuts, cashew nuts, pecans, Brazil nuts, pistachios and macadamia nuts. As the plant families are different, many people only react to peanuts but not to any tree nuts, and vice versa.
Many people who are allergic to tree nuts are only allergic to one type of tree nut, but some are allergic to more. For example, it’s quite common for people with cashew nut allergy to be allergic to pistachios, and for people with walnut allergy to be allergic to pecans.
Peanut and tree nut allergies are common – they are the most commonly known foods to cause anaphylaxis. About 1 in 50 children and 1 in 200 adults in the UK have a nut allergy.