Food allergies occur when the immune system identifies the proteins in a particular food as harmful to the body, subsequently reacting to try to "fight off" the "harmful" proteins (which are in fact harmless). Tree nuts, among which walnuts are included, are one of the "big eight" allergens that cause 90 percent of all food allergies. While people sometimes outgrow food allergies, tree nut allergies are almost always life-long. Nut allergies can be severe and even life-threatening.

Some symptoms of a walnut allergy include:

  • Itching or swelling of the mouth, tongue or lips
  • Skin reactions (eczema, hives, swelling and redness of the extremities or face)
  • Gastrointestinal symptoms (abdominal pain, nausea, vomiting, diarrhea)
  • Respiratory symptoms (runny or stuffy nose, coughing, sneezing, wheezing, difficulty breathing)
  • Cardiovascular symptoms (a drop in blood pressure, lightheadedness, fainting)

If you experience symptoms of anaphylaxis, which include nausea, vomiting, weak or rapid pulse, difficulty breathing, confusion and loss of consciousness, seek immediate medical attention, as this can be fatal.

Walnut allergy symptoms may occur from consuming a tiny amount of the allergen, or just from touching something containing trace amounts of it. There may be trace amounts of walnuts in a product, even if walnuts are not an ingredient in the product, due to cross-contamination during the manufacturing process. Read labels carefully to find out if a product may contain traces of walnuts. Allergic reactions to nuts occur most commonly from cookies, candy, chocolates, granola bars and ice cream. There may also be traces of nuts in cereals, sauces, specialty coffees and liqueurs, shampoos, lotions, bath products and pet food. The pecan is in the same family as walnuts so if you have a walnut allergy it's possible you may be allergic to pecans as well.