Peanut allergy is one of the most common food allergies and is the leading cause of deadly food allergy reactions. Shaking hands with someone who has handled peanuts, or even smelling peanuts, can produce an allergic reaction in some people. For some people, the reaction is so severe that it causes fatal anaphylaxis.
Peanuts are used in a variety of processed foods like ice cream (as a flavoring), marinades, snack foods, biscuits, baked goods, and candy. Certain ethnic dishes also contain peanuts or peanut oil: African, Chinese, Indonesian, Mexican (enchilada sauce), Thai, and Vietnamese cuisines all contain dishes that use peanuts as an ingredient. Some flavorings are nut-based. Peanuts are also used as a thickener in prepared foods. Many roasted and fried foods (including roasted chicken) contain peanut oil.
If you have a peanut allergy, be careful with other types of nuts. Although peanuts are technically a legume (a bean) that grows underground, you may be allergic to nuts grown on trees -- especially almonds, walnuts, hazelnuts, Brazil nuts, and cashews.