photo from CDC

by Reed Mangels, PhD, RD

In the United States, from 2010 to 2022, 110,000 cases of alpha-gal syndrome were reported (1). It’s likely that many more cases went undiagnosed or unreported. Alpha-gal syndrome is a serious, potentially life-threatening allergy to a substance called alpha-gal. This allergy can develop after a tick bite. In the United States, the Lone Star tick is most often the kind of tick whose bite leads to alpha-gal syndrome. In parts of the South, people talk about getting “chigger” bites. “Chiggers,” as they are called are often the larva of Lone Star ticks and can introduce alpha-gal in the same way that mature ticks do (2}. At this time, alpha-gal syndrome is most frequently diagnosed in the southern, central, and eastern parts of the United States (in the area bounded by New York, Iowa, Texas, and Florida), but cases have been reported from other parts of the United States and in other countries (1,3).

Alpha-gal, formally known as galactose-α-1,3-galactose, is a sugar molecule. It is found in most mammals but not in humans. It is also found in in the saliva of some ticks. When those ticks bite a person, their saliva can introduce the alpha-gal into the person’s blood. The person’s body then produces antibodies to the alpha-gal. Then, in some people, when they eat mammals (like cows, pigs, deer, goats) or foods or other substances derived from those mammals (like milk, cheese, or ice cream or certain food additives or medications) those people’s bodies react with the alpha-gal which is naturally found on mammalian cells. This can lead to an allergic reaction, commonly within 2 to 6 hours after eating the meat or dairy product.

Vegans can have alpha-gal syndrome due to a tick bite. Although vegans would not eat meat or dairy products, they could have an allergic reaction to foods that contain meat or dairy or to additives derived from mammals that they are not aware are not vegan. Potentially, a vegan burger cooked on the same grill as a meat burger without the grill being well-cleaned could cause a reaction. Some patients have reported reactions from inhaling alpha-gal from bacon being fried or beef products being grilled (3,4).

The only treatment for alpha-gal syndrome is to avoid meat and other products from mammals that trigger reactions. These reactions could include trouble breathing, dizziness, hives, swelling of the lips/tongue/throat/eyelids, nausea, vomiting, abdominal pain, diarrhea, or decreased blood pressure (1). A serious allergic reaction needs to treated as a medical emergency (5). One death has been reported due to alpha-gal syndrome (2).

Some people with alpha-gal syndrome choose to eat a vegan diet, even though chicken, eggs, and fish do not cause an allergic reaction. They explain that it’s simpler to eat a vegan diet due to concerns about cross-contamination (6). Careful label reading is important for everyone with alpha-gal syndrome because food additives like animal-derived gelatin, meat broth, beef tallow, and lard have the potential to cause reactions. Carrageenan (a substance extracted from sea weeds and used as a food thickener and stabilizer; also found in products like toothpaste), although not a mammalian product, can cause reactions in a small number (estimated 1-2%) of people with alpha-gal syndrome (7,8). You can read more about determining ingredients in medication in the VRG blog post on magnesium stearate.

References

1. Mollah F, Zacharek MA, Benjamin MR. What Is Alpha-Gal Syndrome? JAMA. 2024;331:86.
2. Platts-Mills TAE, Workman LJ, Richards NE, et al. Implications of a fatal anaphylactic reaction occurring 4 hours after eating beef in a young man with IgE antibodies to galactose-α-1,3-galactose. J Allergy Clin Immunol Pract. 2025;13:3422-3424.
3. McGill SK, Hashash JG, Platts-Mills TA. AGA Clinical Practice Update on Alpha-Gal Syndrome for the GI Clinician: Commentary. Clin Gastroenterol Hepatol. 2023;21:891-896.
4. American Academy of Allergy, Asthma, and Immunology. Alpha-gal and Red Meat Allergy. https://www.aaaai.org/tools-for-the-public/conditions-library/allergies/alpha-gal-and-red-meat-allergy. 2025.
5. Mayo Clinic. Alpha-gal Syndrome. https://www.mayoclinic.org/diseases-conditions/alpha-gal-syndrome/symptoms-causes/syc-20428608. 2025.
6. Sempa J, Brenes P, Tegeler A, et al. Alpha-Gal syndrome in the heartland: Dietary restrictions, public awareness, and systemic barriers in rural Kansas. Nutrients. 2025;17:3043.
7. Commins SP. Diagnosis & management of alpha-gal syndrome: lessons from 2,500 patients. Expert Rev Clin Immunol. 2020;16:667-677.
8. Wilson JM, Erickson L, Levin M, et al. Tick bites, IgE to galactose-alpha-1,3-galactose and urticarial or anaphylactic reactions to mammalian meat: The alpha-gal syndrome. Allergy. 2024;79:1440-1454.

To read more about alpha-gal syndrome see:

Alpha-gal Syndrome and Magnesium Stearate and Stearic Acid in Pharmaceuticals: Are They Beef-Derived?

Journal of the American Medical Association Patient Page: What is Alpha-Gal Syndrome?

The contents of this website and our other publications, including The Vegan Journal, are not intended to provide personal medical advice. Medical advice should be obtained from a qualified health professional. We often depend on product and ingredient information from company statements. It is impossible to be 100% sure about a statement, info can change, people have different views, and mistakes can be made. Please use your best judgment about whether a product is suitable for you. To be sure, do further research or confirmation on your own.