Alpha-gal syndrome
Board exam relevance: in 1 of 105 exam reports · rank 181- Synonyms
- red meat allergy, mammalian meat allergy, alpha-gal allergy, tick bite meat allergy, AGS
- Specialty
- Internal medicine · Allergology
- Last updated
- 10/2026 · Dr. Pascal Bafteh
Contents
Definition
Alpha-gal syndrome is an IgE-mediated allergy to the carbohydrate galactose-alpha-1,3-galactose (alpha-gal), which occurs in the meat and products of most mammals. It is a form of red meat allergy. Characteristically, unlike most food allergies, the allergic reactions occur only several hours after eating.
Classification
Distinct from this is the rare pork-cat syndrome, an immediate IgE-mediated meat allergy in which, after primary sensitisation to cat serum albumin (Fel d 2), usually via the airways, cross-reactivity with porcine serum albumin (Sus s 1) leads to reactions within 30 to 60 minutes of eating pork.
Aetiopathogenesis
Alpha-gal is present in most mammals but not in primates, including humans; fish, birds and reptiles do not contain it either. According to current knowledge, sensitisation occurs through tick bites, especially repeated bites: the North American lone star tick (Amblyomma americanum) carries alpha-gal in its saliva. For other tick species too, such as Amblyomma testudinarium in Japan, an association between repeated bites and rising alpha-gal-specific IgE levels has been described.
After sensitisation, foods derived from mammals can trigger an allergic reaction:
- Red meat: pork, beef, lamb and venison.
- Other mammalian products: dairy products and gelatin.
Clinical features
Symptoms often begin only 3 to 8 hours after eating. A pruritic, usually urticarial rash, indigestion, nausea and constipation are typical; anaphylactic reactions also occur.
Diagnosis
- History: delayed allergic reactions after eating meat or dairy products, and previous tick bites.
- Laboratory tests: detection of alpha-gal-specific IgE in serum; the diagnosis rests on the combination of a typical history and this finding.
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Note: Learning content for medical education – not a treatment recommendation and no substitute for diagnosis or treatment decisions in individual cases. Treatment and management are deliberately not covered on this page.