Published: 3 September 2026

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Alpha-gal syndrome: An emerging cause of hypersensitivity reactions to medicines

Published: 3 September 2026
Prescriber Update 47(3): 51–52
September 2026

The Stelara (ustekinumab) data sheet was recently updated to highlight reports of serious hypersensitivity reactions in patients with a history of alpha-gal syndrome (AGS).¹ This article provides information about this rare, but clinically significant, hypersensitivity.

Alpha-gal syndrome (AGS)^2–4

AGS (also called red meat allergy or mammalian meat allergy) is an IgE-mediated allergy to alpha-gal (galactose-α-1,3-galactose). Alpha-gal is a carbohydrate found in the tissues of most non-primate mammals, and in the gut and saliva of ticks. Sensitisation occurs following bites from certain tick species, although the tick species associated with AGS varies geographically.

Once sensitised, a person with AGS may experience hypersensitivity reactions when they consume mammalian products (ie, red meat such as beef, pork or lamb, and other products such as gelatin or milk). Other products containing mammalian-derived alpha-gal (eg, certain biological medicines, vaccines and pharmaceutical excipients) may also cause hypersensitivity reactions in these people. Unlike most food allergies, reactions associated with AGS are typically delayed, occurring 2 to 6 hours after exposure.

Clinical manifestations of AGS range from urticaria, angioedema and gastrointestinal symptoms, to severe anaphylaxis. Diagnosis is based on clinical history and detection of serum alpha-gal-specific IgE antibodies.

AGS and biological medicines

Some biological medicines, including monoclonal antibodies, may contain alpha-gal epitopes.² In patients with AGS, exposure to these medicines may trigger a hypersensitivity reaction.²

Internationally, hypersensitivity reactions have been reported in patients with AGS who received cetuximab, infliximab or natalizumab.² In New Zealand, the Erbitux (cetuximab) and Stelara (ustekinumab) data sheets contain information about AGS and the risk of hypersensitivity reactions.^1,5 The Remicade (infliximab) and Simponi (golimumab) data sheets are being updated.

Consider AGS as a possible explanation for immediate or delayed hypersensitivity reactions associated with medicines, particularly in patients with:^2,3

• a history of tick bites
• a history of delayed allergic reactions following consumption of mammalian products (eg, beef, pork, lamb, gelatin or milk).

Manage suspected anaphylaxis according to local guidelines; treatment discontinuation may be necessary.

References

1. Janssen-Cilag (New Zealand) Ltd. 2026. Stelara New Zealand Data Sheet 2 April 2026. URL: www.medsafe.govt.nz/profs/datasheet/s/stelarainj.pdf (accessed 3 August 2026).
2. Macdougall JD, Thomas KO and Iweala OI. 2022. The meat of the matter: Understanding and managing alpha-gal syndrome. ImmunoTargets and Therapy 11: 37–54. DOI: 10.2147/ITT.S276872. URL: www.tandfonline.com/doi/pdf/10.2147/ITT.S276872 (accessed 14 July 2026).
3. Lesmana, E, Rao S, Keehn, et al. 2025. Clinical presentation and outcomes of alpha-gal syndrome. Clinical Gastroenterology and Hepatology 23(1): 68–78. URL: www.cghjournal.org/article/S1542-3565(24)00672-4/pdf (accessed 15 July 2026).
4. Australasian Society of Clinical Immunology and Allergy (ASCIA). 2024. Mammalian Meat and Tick Allergy: Frequently Asked Questions. URL: www.allergy.org.au/patients/food-allergy/mammalian-meat-tick-faq (accessed 15 July 2026).
5. Healthcare Logistics. 2026. Erbitux New Zealand Data Sheet 22 January 2026. URL: www.medsafe.govt.nz/profs/Datasheet/e/Erbituxinf.pdf (accessed 3 August 2026).