Dear Doctor: I got bitten by a tick, and my doctor said it might make me allergic to meat. That was a few months ago, and I can still eat a hamburger and not get sick. How long does it take for the allergy to start? Will it ever go away?
Dear Reader: It sounds as though you were bitten by Amblyomma americanum, commonly known as the Lone Star tick. Adults are reddish-brown in color, with a rounded body. Females have a single white splotch at the center of their backs, the distinctive “star” that gives the arachnid (that’s right, ticks are not insects) its name. Males have white markings around the edge of their bodies, sometimes in the shape of a horseshoe, but these are often not as noticeable.
Entomologists say the Lone Star is an aggressive tick that actively seeks out its prey. It’s abundant throughout the southeastern United States, and is found along the Eastern Seaboard. As is happening with many species of tick in the U.S., the Lone Star tick has been steadily moving north and west, gradually expanding its range.
As your doctor explained, a growing body of evidence suggests that this species of tick can cause those who have been bitten to develop an allergy to red meat. Specifically, the tick bite causes the immune system to become sensitized to a sugar molecule found in most mammals, but not in humans. Known as galactose-a-1,3-galactose, it’s commonly referred to as alpha-gal. Symptoms of alpha-gal syndrome include hives, rash, nausea, stomach pain that can become severe, difficulty breathing, dizziness, and swelling of the lips, mouth or throat. In rare cases, a severe and potentially fatal allergic reaction known as anaphylaxis is possible.
Unlike in other food allergies, such as to nuts or eggs or shellfish, which trigger a reaction within minutes of consumption, the symptoms of alpha-gal syndrome typically take anywhere from three to six hours to appear. Researchers suspect this is because the allergy is to a sugar molecule rather than to a protein. Also, it appears likely that the meat must be digested in order to release the alpha-gal molecules. This delay can make connecting the symptoms to their cause a challenge.
Not everyone who gets bitten by the Lone Star tick will go on to develop a meat allergy. The syndrome is so new that the interval between the tick bite and the onset of a meat allergy remains unclear. However, data suggests it can range from two weeks to several months. You can get a definitive answer regarding your status by having a simple blood test, which looks for the presence of IgE antibodies, which are specific to alpha-gal. As for how long the allergy lasts, again, no one knows for sure. There is evidence that, barring subsequent Lone Star tick bites, which would reactivate the immune system, the meat allergy can fade over time. Alpha-gal is not normally found in fish or birds, which means anyone who develops the syndrome can safely eat fish and poultry.
(Send your questions to firstname.lastname@example.org, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)