19/04/2026
Alpha-gal syndrome is a delayed allergic reaction to the sugar galactose-α-1,3-galactose (alpha-gal), found in the meat and tissues of most mammals (beef, lamb, pork, venison), but not in humans and apes. Symptoms typically occur 3 to 8 hours after ingestion (unlike most food allergies and making it difficult to initially diagnose) and may include urticaria, gastrointestinal symptoms or even anaphylaxis. The condition is usually triggered by bites from certain ticks, most notably the Lone Star tick (Amblyomma americanum) in the United States, although other tick species in Europe and Australia have also been implicated. While red meat is the main trigger, some sensitised individuals also react to dairy products, gelatine or other mammalian-derived ingredients, reflecting the presence of alpha-gal in these foods. The syndrome appears to be on the increase as tick populations expand and human exposure to tick habitats increases, leading to more frequent sensitisation. I now have two patients with confirmed alpha-gal syndrome.
The mechanism of alpha-gal syndrome is unusual because it is an IgE-mediated allergy to a carbohydrate rather than a protein. After a tick bite, alpha-gal present in tick saliva is introduced through the skin. When the tick bites, it does not just introduce alpha-gal, but also a mixture of salivary proteins, lipids, and immunomodulatory factors that suppress our normal defensive inflammation and instead favour a T-helper-2 (Th2) immune response. As a result, some people develop IgE antibodies against alpha-gal. When mammalian meat, dairy, gelatine or other alpha-gal-containing products are later consumed, the carbohydrate is absorbed on lipid particles (chylomicrons) and enters the bloodstream more slowly than typical food allergens, helping explain the delayed onset of symptoms several hours after eating. Binding of alpha-gal to IgE on mast cells and basophils then triggers histamine release, producing the allergic reaction.
Recently, some people with alpha-gal syndrome have reported reactions to certain non-animal ingredients, most notably carrageenan. This is a sulfated polysaccharide extracted from red seaweed and widely used as a thickener and stabiliser in plant-based milks, processed foods and supplements. Carrageenan does not contain alpha-gal itself, but its galactose-rich structure might cross-react immunologically in highly sensitised individuals.
Among 562 unique patients with self-reported alpha-gal syndrome, allergy to carrageenan was reported by 10.9% of patients. “The challenge is that many alpha-gal patients may not be aware of carrageenan or that it could potentially be an allergen for them”, said Tina Merritt Meinholz, MD, allergist and immunologist at Allergy & Asthma Clinic of Northwest Arkansas in Bentonville, Arkansas, and one of the study’s co-authors.
“So you could get a non-dairy ice cream because you are allergic to ice cream, and the non-dairy ice cream probably has carrageenan as a thickener,” Meinholz told Medscape Medical News. Meinholz added that carrageenan needs to be considered as a potential ingredient and allergen if a patient reacts to a drug but does not appear to have any allergies to other ingredients in that drug. One example is dabigatran, a common generic blood thinner; some versions of dabigatran contain carrageenan, while others do not.
“Drug excipient transparency is a critical patient safety issue in the setting of alpha-gal syndrome,” Sachin A. Shah, PharmD, co-founder of Pill Clarity and professor of pharmacy at the University of the Pacific, Stockton, California, told Medscape Medical News.
Mario Rodenas, associate professor of medicine and director of the clinical elective in allergy and immunology for medical students at Yale University urged some caution in interpreting the results of the study, given that the allergies were self-reported and no test results were presented, a limitation noted by the authors as well.
“While there is some merit in creating awareness of the possibility of someone having an allergy to carrageenan, it is difficult to know if these individuals who self-report an allergy to it do not have some other underlying disorder that can explain their reactions,” Rodenas told Medscape Medical News. “It would have been interesting to know whether they had any blood testing or skin testing to confirm their symptoms are attributable to carrageenan.”
For more information see: https://www.medscape.com/viewarticle/carrageenan-potential-allergen-patients-alpha-gal-syndrome-2026a10007xw?ecd=wnl_conf_allergy_AAAAI-non-spon_260320_mscpedit_etid8197425&uac=48709HJ&impID=8197425
