Tree nuts are nuts that grow on trees.   They include almonds, cashews, hazelnuts (also called filberts), pecans, pistachio, and walnuts.  Peanuts are in a different category (legume family) since they grow underground.   Up to half of individuals allergic to peanuts will also be allergic to tree nuts.    

Some individuals with hay fever can be allergic to pecan and walnut trees.    Here, the individuals are allergic to the pollen of the trees- not the nuts themselves.    There is no cross-reactivity between pollen from pecan/walnut trees and the nuts of these trees.

One of the biggest difficulties with nut avoidance has to do with cross-contamination.   Dishes and foods can be contaminated with nuts during processing and cooking.   This is especially true in restaurants.    Make sure to tell the waitperson about your food allergy and request that clean cooking utensils and pans be used when preparing your food.

Tree nut avoidance

Avoid foods that contain:

• Almond
  
• Almond paste nougat
  
• Brazil nut
  
• Cashew
  
• Chestnut
  
• Filbert
  
• Gianduja
  
• Hazelnut
  
• Macadamia nut
  
• Marzipan
  
• Natural almond extract
  
• Nu-Nuts artificial nuts
  
• Nut butter
  
• Nut oil
  
• Nut paste
  
• Nutella
  
• Pine nut
  
• Pistachio
  
• Walnut
  

These foods may contain tree nuts

• Barbecue sauce
  
• Cereals
  
• Cookies
  
• Flavorings
  
• Ice cream
  
• Mortadella (smoked sausage)
  

Did you know?

Nutmeg is safe to eat.   Although the name would lead one to believe it is made from nuts, it is actually made from the seed of the fruit that is grown on a tropical evergreen called Myristica fragrans.    

Also note that Water Chestnut (often found in Chinese food) is safe to consume and should not be confused with chestnut.

What about coconuts?
There is some confusion as to whether coconuts should be classified as nuts or drupes (which also include walnuts and almonds).  

Regardless of the classification, what really matters is whether there is cross-reactivity between tree nuts and
coconuts.   

What is known so far is that coconut allergy is a rare allergy - only a few case reports have been published.  In some cases, but not all, the individuals also had tree nut allergies and cross-reactivity between these foods was detected during testing.  

Thus, to be safe, individuals with tree nut allergies may want to be tested to coconut allergy before consuming them.