What is Alpha-gal Syndrome?

The Mammalian Meat Allergy

Alpha-gal syndrome 

(AGS), also known as mammalian meat allergy, is an allergy involving an IgE antibody response to galactose-α-1,3-galactose (alpha-gal), a sugar found in all mammals except for old world monkeys, apes, and humans [1]; it is associated with tick bites [3].

Alpha-gal syndrome was first described in 2008 [2]. It is poorly understood within the medical community because of its recent discovery and its varied and atypical presentation, including delayed-onset reactions [1].

All cells, tissues, and fluids of non-primate mammals contain alpha-gal. Alpha-gal is found in mammalian meat, organs, and byproducts, as well as the foods, medications, medical products, personal care products, make-up, and cleaning products to which they are added. Carrageenan also contains alpha-gal [54].


Galactose-α-1,3-galactose, or alpha-gal for short, is an oligosaccharide, or sugar. It is a common component of the glycolipids and glycoproteins produced by all mammals except for old world monkeys, apes, and humans. It is also produced by gut bacteria and many human pathogens.

Alpha-gal is also called the “alpha-gal linkage.” The “alpha-gal epitope” is the part of the alpha-gal antigen to which antibodies attach.

A Paradigm-Shifting Allergy

AGS differs from typical allergies in significant ways.

  • It is believed to be triggered by tick bites (3).
  • It is one of only two life-threatening carbohydrate allergies (4)
  • It causes atypical and delayed-onset symptoms (1,5,6).
  • The allergy component of AGS is only one dimension of an immune response with deeper implications (7).

“…there are also patients who have episodes of abdominal pain without any skin involvement. Those cases are a problem because the possibility of food allergy is not obvious, and they can be severe… Other diagnoses that arise less commonly are arthritis and chronic pruritis. Distinguishing [AGS] from chronic hives can be challenging (6).”

A Growing Threat to Public Health

  • The number of people being diagnosed with AGS is rising (8) as tick populations swell and their ranges expand (3,9).  Models suggest that this expansion will continue (10).
  • AGS is already a common allergy in some regions of the U.S. (11).
  • Throughout the South and much of the eastern U.S., AGS is the leading cause of adult-onset allergy and anaphylaxis (12).
  • Due to a lack of physician awareness (13), AGS is underdiagnosed and commonly misdiagnosed (14).
  • Diagnosis tends to be patient-driven, even in areas where AGS is prevalent (14).

In one recent study of anaphylaxis, AGS was found to be the number one trigger, accounting for 33% of the cases with a definitive cause. The number two cause was all other food allergies combined, at 28%. In the same study, recognition of AGS led to a reduction in the percentage of anaphylaxis cases without a definitive cause from 59% to 35% of total cases (44).

For more information about the growing AGS epidemic see An Emerging Epidemic


How Do You Get Alpha-gal Syndrome?

  • Alpha-gal syndrome is believed to be triggered by the bite of certain species of ticks. In different parts of the world, different tick species are responsible (15).
  • In North America, the bite of the Lone Star Tick (Amblyomma americanum) thought to be the trigger (16).
  • It is likely that additional as of yet unidentified tick species (8), maybe other ectoparasites, like chiggers (17), and possibly even endoparasites (3,18) can trigger AGS.
  • Alpha-gal has been found in the saliva of Black-Legged Ticks (Ixodes scapularis) (8). It is likely that Black-legged Ticks can trigger AGS, as do other species in their genus, but this has yet to be demonstrated.
  • The Asian Longhorned Tick (Haemaphysalis longicornis), recently introduced in the U.S., is known to trigger AGS in Asia (19). As of yet, it has not been tied to any cases in the U.S, but it seems likely that it will be.
  • Only some people who are bitten by ticks that can trigger AGS actually develop it (6).
  • Even if you have been bitten by ticks before and did not develop AGS, a future bite could trigger it (3)..
  • Repeated tick bites are associated with a rise in alpha-gal IgE (20).
  • Multiple tick bites are associated with the onset AGS (3). Many patients report that they were bitten by ticks for many years, and then after being bitten by multiple ticks at once, they developed AGS.

What Is Alpha-gal Found In?

Alpha-gal is found in the tissues, cells, and fluids of mammals (1) as well as products containing mammalian-derived ingredients. These include (but are not limited to):

  • Mammalian meat (1), such as beef, pork, lamb, bison, venison, goat, rabbit, squirrel, groundhog, moose, elk, kangaroo, antelope, buffalo, etc.
  • Mammalian organs, including liver (21), kidneys, and intestines contain even more alpha-gal than mammalian meat (222324, 25, 26, 27)
  • Milk, dairy products (1,22) gelatin (27,28), and other foods with mammalian-derived ingredients, including many processed foods (2229)
  • Other mammalian products and byproducts
  • Cetuximab (a drug that played a role in the discovery of AGS) (30, 31), heparin, pancreatic and other enzyme replacements (36), drugs with gelatin capsules or mammalian-derived inactive ingredients, like some magnesium stearate, and many perioperative, prescription and OTC drugs (632, 3334, 353637, 38)
  • Many vaccines, including those that contain gelatin such as Zostavax and MMR and others (2835363940414243)
  • Many medical products and devices, including (but not limited to) some bioprosthetic heart valves (4546, 47, 48, 49), antivenoms (5051), plasma volume substitutes (28, 52), hemostatic agents (53), catgut sutures, topicals, adhesives, etc. (6,32, 3334, 3536,).
  • Many personal care and household products, such as those containing “hydrolyzed protein” (gelatin), lanolin, glycerin, collagen, and tallow.
  • Airborne particles, such as fumes from cooking meat

The food additive carrageenan is not made from mammals, it is made from red algae, but it contains the alpha-gal linkage/epitope (54, 55).

  • Although in a laboratory setting, three forms of carrageenan did not inhibit the binding of IgE to alpha-gal (56), it is well-known within the AGS community that many of us react to it. Anecdotal reports suggest that reactions to carrageenan can be severe and tend to have a more rapid onset than our reactions to alpha-gal in mammalian products.

What Foods Do Not Have Alpha-gal in Them?

Alpha-gal is NOT found in:

  • Fish or seafood.
  • Birds, like chicken, turkey, quail, and emu.
  • Reptiles, like snakes, crocodiles, and lizards or amphibians, like frogs
  • Plants, including all fruits, vegetables, and grains. Note that algae are not plants, and some algae do contain alpha-gal.
  • Some of these foods may be injected with, or otherwise contaminated by, mammalian products, byproducts, or carrageenan, especially chicken, turkey, and seafood.
  • Some people with AGS report reacting to canned tuna (6,), for reasons that are not clear, but may be related to fillers or contamination with dolphin.


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2.  Commins, S. P., et al. (2008). Anaphylaxis and IgE Antibodies to Galactose-Alpha-1,3-Galactose (alphaGal): Insight from the Identification of Novel IgE ab to Carbohydrates on Mammalian ProteinsJournal of Allergy and Clinical Immunology, Volume 121, Issue 2, S25.

3. Commins, S. P., et al. (2011). “The relevance of tick bites to the production of IgE antibodies to the mammalian oligosaccharide galactose-α-1,3-galactose.” Journal of Allergy and Clinical Immunology 127(5): 1286-1293.e1286.

4. Soh, J. Y., et al. (2015). “Carbohydrates as food allergens.” Asia Pac Allergy 5(1): 17-24.

5. Levin, M., et al. (2019). “Galactose alpha-1,3-galactose phenotypes: Lessons from various patient populations.” Ann Allergy Asthma Immunol 122(6): 598-602.

6. Platts-Mills, T. A., et al. (2019). “Diagnosis and management of patients with the alpha-Gal syndrome.” J Allergy Clin Immunol Pract.

7. Commins, S. P. (2016). “Invited Commentary: Alpha-Gal Allergy: Tip of the Iceberg to a Pivotal Immune Response.” Curr Allergy Asthma Rep 16(9): 61.

8. Crispell, G., et al. (2019). “Discovery of Alpha-Gal-Containing Antigens in North American Tick Species Believed to Induce Red Meat Allergy.” Front Immunol 10: 1056.

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20. Hashizume, H., et al. (2018). “Repeated Amblyomma testudinarium tick bites are associated with increased galactose-α-1,3-galactose carbohydrate IgE antibody levels: a retrospective cohort study in a single institution.” J Am Acad Dermatol 78(6): 1135-1141.e1133.

21. Bianchi, John (2019). Personal communication

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