How a Tick Can Pass You a Horrifying Red Meat Allergy, Explained

Well, this is terrifying: A rare food allergy that blames a tick bite as its reason for onset could be easier for humans to catch than originally thought. The red meat allergy, which some humans develop after being bitten by a tick, manifests like any other food allergy (symptoms vary, ranging from hives to swelling to, yes, anaphylaxis in extreme cases). Allergic parties — now known as alpha-gal syndrome sufferers — are usually unable to consume beef and pork; sometimes, dairy products are also off-limits.

Originally, it was thought that the tick in question would cause the steak-hating immune response only if it bit another, non-human animal first. But as Gizmodo reports, preliminary results from a study presented at an American Academy of Allergy, Asthma and Immunology conference suggest that it’s the tick’s saliva itself that’s causing the no-burgers-for-you reaction.

Wait, how is this possible?

Humans are not born with allergies to alpha-gal, a carbohydrate found in a lot of mammal protein — including in pigs and cows — and for years, doctors were unsure what could cause an allergic reaction in some people when they consumed beef or pork. But as a 2014 New Yorker story chronicles, a 2011 study showed that many people who experience allergic reactions to alpha-gal had been previously bitten by ticks. Scientists theorized that the ticks’ saliva could “mimic” the blood sugar of its prior meal, and if, for example, the tick bit a cow before biting a human, the human body’s immune system would treat that saliva as a foreign antigen and react appropriately — ie, with an allergic reaction.

The new research presented at the AAAAI conference, however, suggests that it doesn’t matter what, if anything, a tick has bitten before feasting on a human, and that the alpha-gal reaction is from the tick’s saliva itself. The research has not been published in a peer-reviewed journal yet, but lead researcher Scott Commins tells Gizmodo, “All humans make an existing response to alpha-gal and these data would be consistent with a model where tick bites simply redirect the existing immune response to shift to an allergic one.”

What kinds of ticks could cause this, and how likely am I to be bitten by one?

The Lone Star tick, which resides mostly in the eastern half of the United States and Mexico, is largely blamed for alpha-gal syndrome. But Commins’s recent research saw saliva from deer ticks — which can be found in the eastern and northern Midwestern U.S., and is the main carrier of Lyme disease — also triggering an allergic reaction.

The Mayo Clinic notes that up until now, “most” cases of alpha-gal syndrome have been reported in the southeast U.S. However, cases have been reported “farther north and west... as deer carry the Lone Star tick to new parts of the United States.” And if deer tick saliva can also cause a reaction to alpha-gal, it’s likely more cases can be found in the northeast and parts of the Midwest.

Okay, great, so how likely am I personally to have this no-meat reaction?

The odds of you having an allergic reaction to alpha-gal from a tick bite is rare — at least in comparison to the other health complications that ticks cause. Each year, 30,000 Americans are diagnosed with Lyme disease, according to the Centers of Disease Control, while Commins estimated in 2018 that alpha-gal syndrome sufferers — at the hands of a Lone Star tick, anyway — total about 5,000 in the U.S. That said, a 2018 New York Times Magazine investigation reported that in “some tick-heavy regions, the prevalence of meat allergy is estimated to be at least 1 percent of the population.”

What do I do if I think I have this?

Go to a doctor. And in a bit of good news, the allergy might dissipate over time, so long as you’re not bitten by another tick: So there’s hope for future steaks and pork chops, after all.

• Weird Meat Allergy Caused by Ticks May Be Easier to Catch Than We Thought [Gizmodo]
• What the Mystery of the Tick-Borne Meat Allergy Could Reveal [NYT]