We're in the thick of tick season, and that tends to trigger mental associations with Lyme disease. But as the arachnids emerge this year, attention is also being paid to a rare allergy that ticks may be spreading, and it's a carnivore's worst nightmare: itchy hives every time you eat red meat. The ticks implicated in the meat allergy are lone star ticks (Amblyomma americanum)---a different species than the deer ticks which carry Lyme disease. Weeks or months after a bite from the ticks, people have reported a new allergy to beef, pork and lamb with a characteristic slow onset: while most food allergies would be felt instantly after eating, these meat allergies kick in three to six hours after a meal, often in the middle of the night.
Cases of the strange allergy were first reported at the University of Virginia in Charlottesville in 2007. Since then, allergy specialists Thomas Platts-Mills and Scott Commins have documented more than 1,000 cases, from Texas to Massachusetts, of people who report a delayed allergic reaction to red meat. These individuals all have elevated blood antibodies to alpha-gal, a sugar found in meat, and the researchers think the production of these antibodies is triggered by tick bites. Small studies support this claim. In 2011 Platts-Mills and Commins reported that, after tick bites, antibodies to alpha-gal rose twenty-fold
in three individuals after they experienced a first tick bite. (Samples of the individuals' blood had been taken previously, and the participants self-reported tick bites.) In two of the three cases the ticks were identified as A. americanum. This year, they reported that tick bites are strongly implicated as a cause
of the allergy. However the bites don't appear to be the only cause: not everyone's who is bitten by the lone star tick develops the antibodies. In Pediatrics last month the scientists reported
that 45 children in the Lynchburg, Va., area display the allergy as well as elevated alpha-gal antibodies; most reported being bitten by ticks within the past year. "This tick is very aggressive," Platts-Mills told NPR
. "Its larval forms will bite humans, whereas none of the other American tick larvae will do that." Fortunately, the allergic reaction seems to fade after a few years, the Wall Street Journal reports
, provided that the individual doesn't get bitten again. Images courtesy CDC