Ask the Doctors

Dear Doctor: What's the deal with the tick bite that makes you allergic to meat? Will I know if it happens to me?

Dear Reader: Sounds like science fiction, right? A single tick bite scrambles your immune system so that overnight you become allergic to foods you've been eating your entire life. But unfortunately for a small but growing number of people in the United States, this scenario is all too real.

The culprit is the Lone Star tick, which is widely distributed throughout the Eastern, Midwestern and Southeastern states. Recent studies suggest that the tick may be on the move. It has been identified as far north as New York state and Maine, and as far west as Texas. It gets its name from the single splotch, or "star," that the adult female has on her back.

It was in 2009 that scientists first began to connect the dots between the Lone Star tick and a rather unusual immune response. Certain people who were bitten by the tick went on to develop a sudden and sometimes quite serious allergy to red meat. This includes beef, lamb and pork.

Something in the tick bite sends alarm bells ringing in the immune system, ordering it to target a specific carbohydrate found in meat. The full name is galactose-alpha-1,3-galactose, but it's commonly shortened to alpha-gal.

The specific agent that causes the allergy, be it a microbe or a biological compound found in the tick's saliva, is under study. So far scientists have been left with far more questions than answers. This includes whether the sensitivity to alpha-gal can be reversed.

In most food allergies, the physical response is swift. Eat a strawberry and a few minutes later, you break out in hives. With the alpha-gal allergy, however, it can take the body up to 12 hours to react. The slow onset of alpha-gal allergy symptoms can make the diagnosis a challenge.

The most common symptoms are stomach pain, nausea, hives, skin rash, sneezing, headaches and wheezing. In severe cases, anaphylactic shock is possible. The allergic reaction can happen after just a single bite of meat. It has also been observed in people taking medications that contain gelatin, as well as those using new cancer drugs derived from genetically modified mice.

The recent spread of the alpha-gal allergy beyond the traditional borders of the Lone Star tick's range has scientists questioning whether other species of ticks may also be involved. If you've recently been bitten by any tick and suspect you may have developed an alpha-gal allergy:

-- Stop eating red meat or any other foods that trigger symptoms.

-- Know that some symptoms can be controlled with antihistamines and corticosteroids.

-- For severe reactions, including anaphylaxis, use injected epinephrine, which requires a prescription.

For an accurate diagnosis, make an appointment with an allergist. He or she will want to know:

-- What you ate that triggered the symptoms.

-- The time frame in which symptoms appeared.

-- The specifics of the symptoms and how long they lasted.

A blood or skin test will show whether food-specific antibodies are present. Your allergist will use the results of these tests to arrive at a diagnosis.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

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