Whenever I give talks about Lyme disease, people ask, “What about that other tick-borne disease I keep hearing about, the one that makes you allergic to meat? Is that really a thing?”
Unfortunately, it is. It’s called alpha-gal syndrome, and it’s caused by the bite of a lone star tick. Let’s walk through what alpha-gal syndrome is, how you get it, how it’s diagnosed, and what you can do about it.
Alpha-gal syndrome, also called mammalian meat allergy, is an allergy to red meat and other mammalian products such as dairy. When a lone star tick bites you, its saliva can transmit a sugar molecule called alpha-gal into your blood. Because humans don’t otherwise have this sugar molecule, some people’s immune systems create antibodies against it. When the person eats red meat, those antibodies trigger an allergic reaction.
Alpha-gal syndrome causes allergic reactions such as severe digestive issues (cramping and pain, nausea, diarrhea, vomiting) and/or hives, itching, or swelling. In some cases, it can cause anaphylaxis. The level of allergic reaction varies per patient. Some have digestive issues, some react only to red meat but not dairy, and some react to both. Each reaction can be different, so if you’re diagnosed with alpha-gal syndrome, you should carry an epi-pen in case of a severe reaction to accidental exposure. Unlike many food allergies, alpha-gal syndrome symptoms aren’t immediate; they can take 2–6 hours to appear, making it harder to connect reactions to specific meals.
Like Lyme disease, alpha-gal syndrome is a clinical diagnosis that can be corroborated by a blood test. A diagnosis should be made on symptoms and timing (i.e., if you develop an allergic reaction a few hours after eating red meat) as well as risk factors (whether you’ve spent time in an area where lone star ticks are prevalent). Remember that ticks are on the move, and that people travel—even if you don’t live in an area where ticks are endemic, consider whether you’ve traveled to someplace where they are.
Alpha-Gal Syndrome is on the rise. Between 96,000—450,000 people may have developed alpha-gal syndrome since 2010. The estimate is wide because AGS is not nationally reportable and likely underdiagnosed, due to delayed symptom onset and variation in how it presents.
Although typically associated with southern U.S. states, the lone star tick has also moved north across the Eastern U.S., most recently descending upon the island of Martha’s Vineyard, as described in The New York Times article “Why Is Martha’s Vineyard Going Vegan? It’s All About Tick Bites.”
If you are diagnosed with alpha-gal syndrome, you should avoid red meat and potentially dairy if it affects you. Carry an epi-pen in case you accidentally are exposed and have an anaphylactic reaction. Some people even report being affected by fumes of red meat that is cooking.
The chances of that happening from the same tick bite are very, very rare, because lone star ticks don’t carry the Lyme disease bacteria; black-legged ticks do. There have only been two case reports of black-legged ticks potentially connected to alpha-gal syndrome. If you are bitten by both a lone star tick (triggering Alpha-Gal syndrome) and a black-legged tick carrying Lyme bacteria, then yes, you could develop both conditions, but otherwise they are caused by two different ticks.
Lone star ticks can also cause other illnesses. They can carry pathogens that cause tularemia, Bourbon virus disease, heartland virus disease, ehrlichiosis. Their bites are also associated with Southern tick-associated rash illness (STARI), but the exact cause of STARI is unknown.
The best way to protect yourself from alpha-gal syndrome is to reduce exposure to lone star ticks by being Tick AWARE:
Sources:
https://www.nytimes.com/2025/08/12/dining/marthas-vineyard-alpha-gal-tick-bites.html
https://www.cdc.gov/mmwr/volumes/72/wr/mm7230a2.htm?s_cid=mm7230a2_w
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