Tick bites have long been synonymous with bad news, responsible for transmitting diseases such as Lyme disease, Ehrlichiosis, and Rocky Mountain spotted fever, but this must be a carnivore or BBQ lover's worst nightmare. A growing body of research suggests that bites from a particular tick are causing an unusual allergic reaction to meat. At an allergy meeting last week, for example, a diagnostics lab presented evidence that the highest prevalence of the allergy is in the southeastern United States, where the tick primarily thrives. Yet American BBQ lovers and carnivores elsewhere may not rest easy; the allergy mysteriously afflicts people living in parts of the United States, even Hawaii, where the tick does not live.
The meat allergy, known as alpha-gal for a sugar carbohydrate found in beef, lamb, and pork, produces a hivelike rash—and, in some people, a dangerous anaphylactic reaction—roughly 4 hours after consuming meat. But unlike other common food allergies, the alpha-gal allergy has been found only in people who have been bitten by ticks—specifically the lone star tick, previously best known for causing a condition called southern tick-associated rash illness, the symptoms of which include rash, fatigue, headache, fever, and muscle pains. "You have to have a tick bite to then trigger the immune reaction," Stanley Fineman, an allergist and president of American College of Allergy, Asthma and Immunology (ACAAI).
People who are bitten by the ticks develop antibodies against the alpha-gal sugar, and individuals with symptoms can be diagnosed by a blood test that looks for the presence of those antibodies. But Fineman says that too few people are aware of the allergy or don't make the connection between a case of hives and the meal they had much earlier in the day, and so they never get tested. "It takes 4 to 6 hours to see a reaction, so many people don't correlate that to their meat, or hamburger or something. It's easy to miss," Fineman says.
Allergy researcher Thomas Platts-Mills of the University of Virginia (UVA) in Charlottesville has been studying the alpha-gal reaction since 2002, when he began investigating an unusual sensitivity to the cancer drug cetuximab, which contains the same alpha-gal sugar as meat. Cancer patients who demonstrated an allergic reaction to the drug were nearly exclusive to the southeastern United States and were also found to have high levels of alpha-gal antibodies, Platts-Mills explains. Furthermore, some of them, along with other noncancer patients in the same region, also reported having severe allergic reactions after eating meat. Platts-Mills later published the relationship between alpha-gal antibodies and the cetuximab allergy in The New England Journal of Medicine.