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ACAAI > Patients & Public > Resources > Ask the Allergist

Can tick bites cause food allergies?

Q. During her college year in South Carolina, my 20-year-old daughter was bitten by ticks on three separate occasions. With the most recent bite, after the tick was removed for several days she noticed local itching and a rash at the site of the bite. Recently she has developed a series of unexplained allergic reactions that always seem to start 3-5 hours after a meal. Typically, about 4 hours after eating she complains of a stomachache, itching of her skin all over, hives and swelling of her lips and tongue. One time, the mouth and tongue swelling were so severe we took her for treatment in the emergency room because we were concerned she would be unable to breathe. On that occasion, the doctors treated her with epinephrine. We pinpointed that these reactions seem to occur after eating any beef, lamb or pork but not when she avoided those foods. However, now she continues to have these reactions, hours after eating, but despite avoidance of beef, lamb and pork. We are puzzled. Are these serious reactions caused by foods or something else?

A. Based on the brief description of your daughter's medical reactions it is possible that she developed allergy to galactose-alpha-1,3-galactose (called "alpha-gal"), a carbohydrate found in beef, lamb, and pork food products. Systemic allergic reactions related to this allergy have been widely reported and can even present as anaphylaxis, a potentially life-threatening allergic reaction with difficulty breathing, decreased blood pressure, and other symptoms requiring emergency treatment and epinephrine.

Strangely, this has been a problem for individuals living in the southeastern United States who have received bites from the lone star tick (Amblyomma americanum) found in this part of the country. Although not completely understood why, patients who have received bites from these ticks are at greatest risk for developing allergy to alpha gal. The alpha gal is contained in all red meats. In some cases affected patients also have delayed allergic reactions to beef or pork gelatin or even cow's milk, which may contain alpha gal. Typically with this type of allergy there is an unexpected 3 to 5 hour delay between meals and the beginning of the generalized allergic reaction. For this reason, it has been difficult for doctors and patients to make a connection with these foods. As in your daughter's case, it may not be adequate just to avoid red meat to prevent reactions. It also may be necessary to stay away from products such as beef and pork gelatin and sometimes milk products.

Allergic reactions are caused by allergic antibody (IgE antibody). This unusual and complex problem is best evaluated by a board certified allergist in your area, who can perform testing for allergic antibodies to alpha gal, beef, pork and lamb. Once a diagnosis is established, strict dietary avoidance of all causative foods is effective treatment.

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