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Key takeaways
- Positive tests for alpha-gal syndrome have increased in recent years.
- Symptoms can appear hours after eating meat, making the allergy harder to spot and diagnose.
- Experts say preventing tick bites is key to avoiding the allergy.
A growing number of Americans are developing an unusual but serious allergy to red meat after a tick bite.
Positive test results for what’s known as alpha-gal syndrome increased by 100-fold between 2013 and 2024, according to a 2025 study published in The American Journal of Gastroenterology. And a 2023 report from the Centers for Disease Control and Prevention (CDC) says that as many as 450,000 people in the United States may have been affected by alpha-gal since 2010.
It’s “an important emerging public health problem, with potentially severe health impacts that can last a lifetime for some patients,” said Ann Carpenter, an epidemiologist and an author on the CDC report. And it’s critical for doctors and health care providers to be aware of it, so they can properly educate, diagnose and manage their patients, she added.
Alpha-gal’s rise coincides with a spike in other tick-borne diseases, which more than doubled between 2004 and 2016, federal data shows. The alpha-gal allergy can be triggered weeks after a bite from the lone star tick and possibly other varieties.
“We’re continuing to identify new patients every week in allergy clinics across the Southeast and East who’ve had, essentially, brand-new reactions,” says Dr. Scott Commins, professor of medicine at the University of North Carolina and a leading expert on alpha-gal syndrome. “And that has been a big change over the past, say, 10 years.”
What is alpha-gal?
Alpha-gal is a sugar molecule — many mammals have it, including cows and pigs, and Commins says researchers have come to understand that some ticks do too. But it’s not found in people, so when a person gets a bite from a tick that has alpha-gal in its saliva, the body creates an immune response to the molecule, and some people have a strong allergic response.
“So then when we eat a hamburger, hotdog, etc., we have an allergic reaction to the meat, and it’s specifically to that alpha-gal that’s in pigs and cows,” Commins says. This is the case even if a person has been able to eat red meat their whole lives without a problem.
Recognizing the symptoms of alpha-gal
Unlike with other food allergies, symptoms of alpha-gal syndrome don’t come on right away.
“If you have a peanut allergy and you go out to a restaurant and you get an accidental exposure, you know you’re in trouble before you leave the restaurant,” says Dr. Jeffrey Wilson, an allergist and immunologist at UVA Asthma, Allergy and Immunology.
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