Allergic Reactions to Walnuts

Skin prick allergy test
An allergist testing a client in a lab. (Image: AlexRaths/iStock/Getty Images)

Nine of every 10 food allergies results from sensitivity to any one of eight foods, the U. S. Food and Drug Administration reports. Tree walnuts and other tree nuts are among these eight food allergens. A walnut allergy typically lasts a lifetime. Walnuts can show up in baked goods, liqueur, candy, pesto, ice cream, salad dressings or toppings, and trail mixes. Walnut oil, although a good source of healthful omega-3 fatty acid, also can trigger allergies. Symptoms of a walnut allergy range from mild to life-threatening.

Cause of Reaction

About 1.8 million people in the United States experience allergies to tree nuts, the Food Allergy and Anaphylaxis Network reports. Like other tree nuts, walnuts can cause a range of unpleasant reactions. Problems arise when your immune system mistakes walnut protein for a harmful substance and releases antibodies into your bloodstream to destroy it. These antibodies stimulate specific cells to produce histamines and other chemicals. Histamines cause the skin, digestive and respiratory symptoms generally associated with allergies. Fewer than 10 percent of tree nut allergy sufferers outgrow their condition, according to the American College of Allergy, Asthma and Immunology.

Symptoms

Symptoms of allergic reactions to walnuts usually appear no more than four hours after exposure. They often surface within a few minutes. Hives around the mouth that spread to other parts of your body are typical early signs. Rashes and swollen eyelids often follow, along with watery eyes and nasal congestion. Diarrhea or vomiting, wheezing, labored breathing and asthma attacks may occur. Simply touching walnuts can trigger allergic responses in some people. If walnut proteins enter your skin through a wound, the reaction can equal or exceed that from consuming them. Allergic symptoms usually subside within 24 hours.

Anaphylaxis

Some allergic reactions progress to anaphylaxis, a serious and possibly life-threatening condition. Anaphylaxis is a state of shock that requires immediate treatment. Signs of anaphylaxis include a faint, rapid pulse; clammy, cold skin; respiratory distress; and fainting. People with known walnut allergies should always carry injectable epinephrine, widely available with a doctor's prescription, for use at anaphylactic onset. A medical bracelet identifying the condition can also be a lifesaver.

Managing Walnut Allergy

Walnuts and pecans belong to the same tree nut family. An allergic reaction to them does not necessarily indicate corresponding allergies to nuts of other families. All tree nuts, however, may be exposed to traces of walnuts during processing, because they frequently are processed on the same equipment. The only way to determine the extent of an allergy is through testing. An allergist may perform skin or blood tests, or prescribe an avoidance diet to determine whether an allergic reaction is walnut-related. If so, avoiding walnuts, pecans and any food containing them or traces of them is the only way to prevent allergic reactions.

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