A tiny tick might be to blame for a rash of meat allergies in central and southern regions of the U.S.
A bite from the lone star tick, so-called for the white spot on its back, looks innocent enough. But researchers say saliva that sneaks into the wound might trigger a reaction to meat agonizing enough to convert lifelong carnivores into wary vegetarians.
"People will eat beef and then anywhere from three to six hours later start having a reaction; anything from hives to full-blown anaphylactic shock," said Dr. Scott Commins, assistant professor of medicine at the University of Virginia in Charlottesville. "Most people want to avoid having the reaction, so they try to stay away from the food that triggers it."
Cases of the bizarre allergy are cropping up in areas ripe with lone star ticks, according to research presented today at the American College of Allergy, Asthma and Immunology annual meeting in Anaheim, Calif. But whether the bugs cause meat allergies remains unclear.
"It's hard to prove," said Commins. "We're still searching for the mechanism."
Allergies are immune reactions to foreign substances, from pet hair to peanuts. As antibodies attack the substance that caused the reaction, they trigger the release of histamine, a chemical that causes hives and, in severe cases, life-threatening anaphylaxis.
Commins said blood levels of antibodies for alpha-gal, a sugar found in beef, lamb and pork, rise after a single bite from the lone star tick. He said he hopes experiments that combine tiny samples of tick saliva with the invisible antibodies will prove the two are directly connected.
"It's complicated, no doubt," said Commins. "But we think it's something in the saliva."
The long lag between exposure to meat and the allergic reaction complicates things even more.
"Most food allergies occur very quickly," said Dr. Stanley Fineman, president of the American College of Allergy, Asthma and Immunology. "It's also a bit unusual to see adults develop a food allergy."
But the tick bite theory could help explain the sudden onset of some meat allergies, Fineman added.
Other Common food allergens include peanuts, shellfish, milk, eggs, soy and wheat. And most food allergy sufferers are glad to discover the source of their misery, even if it means upheaval for their diets.
"Avoidance is the best way to handle any food allergy," he said.
But meat allergies are hard for some brawny barbecuers to swallow.
"Some people are totally destroyed," said Commins. "Others say, 'Maybe I'm better off without it.'"
- food allergies