This last August, The New York Times published an article entitled “Why Is Martha’s Vineyard Going Vegan? It’s All About Tick Bites.”
(https://www.nytimes.com/2025/08/12/dining/marthasvineyard-alpha-gal-tick-bites.html)
Tick bites can induce “alpha-gal syndrome,” which is an allergy to red (mammal) meat and can include reactions to dairy and other animal products as well. The prevalence of this allergy is increasing remarkably all across the country. I have it, as does my son-in-law and several friends. There are some peculiarities to this allergy syndrome that make it important to know about — even if you don’t have it. Yet.
Key points
- Symptoms associated with alpha-gal can vary from mild/moderate GI pain, diarrhea, hives, and angioedema to anaphylaxis (throat swelling, difficulty breathing, loss of consciousness, low blood pressure, shock). The most common symptoms are cutaneous (e.g., hives, 70–90%) and gastrointestinal symptoms (70+%), although roughly one-third to one-half of cases (depending on samples reported) also involve symptoms of anaphylaxis.
- The mechanism of sensitization and development of the allergy process is not well established. One fun fact: the presence of anti–alpha-gal antibodies can protect against malaria. They may also protect against mycobacterial infections.
- The leading hypothesis involves tick saliva (yes, ticks have saliva!) that contains alpha-gal, which, especially as the tick “continues to feed” (!!), comes in contact with immune cells, activating the pathway to allergy. Many different ticks worldwide can induce alpha-gal syndrome in humans.
- Sensitization to alpha-gal (a carbohydrate) does not necessarily induce symptoms, and titers of antibody (IgE) don’t correlate well with symptom severity. This ambiguity makes it hard to predict the risks and course of any case of alpha-gal syndrome. Clearly, there are other factors involved.
- Interestingly, though, a study of 1,112 adults who reported GI symptoms found that about one-third had low levels of circulating alpha-gal. A follow-up of 112 of the alpha-gal–positive people reported improvements in symptoms “reminiscent of irritable bowel” in 82% of those who eliminated red meat from their diet. So low levels of alpha-gal titers may not be benign and could account for unexplained GI symptoms.
- Risk factors identified for the allergy include being male; hypersensitivity to medications including the cancer chemotherapy agent cetuximab and medications that contain gelatin; A and O blood types (most of us); a history of bioprosthetic bovine/porcine heart valves; rural outdoor jobs; and a history of idiopathic (unexplained) anaphylaxis.
- Alpha-gal syndrome is the leading cause of anaphylaxis in the southern U.S. Interestingly, “idiopathic anaphylaxis” cases seem to be declining while alpha-gal–induced anaphylaxis cases are increasing, suggesting that many cases of “idiopathic anaphylaxis” may have actually been undiagnosed alpha-gal reactions.
- Unlike most food allergies, in which symptoms manifest within minutes, alpha-gal symptoms usually take at least two to three hours. How fast the symptoms appear may relate to the amount of alpha-gal in the food. For instance, organ meat is very rich in alpha-gal. Alcohol consumption and exercise may also speed up the process.
- Management of alpha-gal syndrome centers on avoiding red meat, especially organ meats and fattier cuts of meat. This may seem easy, but there can be hidden sources of alpha-gal in medications and commercial foods such as bacon, lard, beef broth, and even in casings for poultry or “vegetarian” sausages.
- Dairy does not need to be routinely avoided unless the person reacts to it in the strict absence of any other potential alpha-gal source (about 20% of cases). In those cases, dairy must be strictly avoided. For non–dairy-sensitive alpha-gal syndrome, moderate intake of dairy was associated with an increased likelihood of spontaneous remission.