Peanuts are not the same as tree nuts (almonds, cashews, walnuts, etc.), which grow on trees. Peanuts grow underground and are part of a different plant family, the legumes. Other examples of legumes include beans, peas, lentils, and soybeans. If you are allergic to peanuts, you do not have a greater chance of being allergic to another legume (including soy) than you would to any other food.
Trace amounts of peanut can cause an allergic reaction. Casual contact with peanuts, such as touching peanuts or peanut butter residue, is less likely to trigger a severe reaction. Casual contact becomes a concern if the area that comes into contact with peanuts then comes into contact with the eyes, nose or mouth (for example, a child with peanut allergy gets peanut butter on her fingers, and then rubs her eyes).
Based on recent studies, an estimated 25-40 percent of people who have peanut allergy also are allergic to tree nuts. In addition, peanuts and tree nuts often come into contact with one another during manufacturing and serving processes. For these reasons, allergists usually tell their patients with peanut allergy to avoid tree nuts as well.