Alpha-Gal Syndrome

By Wayne Persky

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Alpha-gal syndrome (AGS) — the tick-borne allergy to mammalian meat and other animal products, is no longer a regional curiosity. Experts report that cases are moving beyond the Mid-Atlantic and South into the Great Lakes and central U.S., with growing recognition worldwide. The message from front-line researchers and the CDC is clear — even if AGS hasn't been discovered in your neighborhood yet, the odds that it soon may be are rising (McKnight, 2025, October 01).1​​

Severity of symptoms can vary among patients.

Galactose-α-1,3-galactose (alpha-gal), is a carbohydrate present in most mammals (although not in primates). In the U.S., tick saliva, most often from the lone star tick (Amblyomma americanum), carries proteins that deliver alpha-gal and trigger IgE-mediated sensitization. Not all bites trigger the development of AGS, and the severity varies. Susceptibility factors remain unclear.

AGS is unusual among food allergies for at least 2 reasons.

1. ​Despite the fact that the reactions are IgE mediated, reactions are delayed by hours after exposure to mammalian products (meat, dairy, gelatin in packaged foods).
2. All other known allergies are directed against proteins — alpha gal is a carbohydrate.

Symptoms include:

• Severe urticaria (hives)
• Diarrhea and abdominal distress
• Cardiovascular issues such as hypotension, chest pain, “cardiovascular collapse, which are more prominent than respiratory features in many cases
• Respiratory symptoms are less common than in classic anaphylaxis, but asphyxiation has been reported in fatal events

​The CDC now warns AGS can be fatal, and has issued its first clinical guidance. Epinephrine should be readily available and used promptly for systemic reactions.

AGS is increasing rapidly.

From the first 24-case description in 2009 to an estimated 450,000 reported cases in the U.S. by mid 2023, recognition of this problem has grown dramatically. Awareness may explain part of the increase, but experts also point to more tick bites, primarily due to expanding deer populations (the main host for lone star ticks), land-use changes that increases human–deer/tick contact, and climate-driven deer tick range expansion.​

Although the lone star tick dominates exposure risk in the U.S., other ticks have been implicated globally (for example, Ixodes ricinus in Europe). Early U.S. data suggest additional species, including the deer tick (Ixodes scapularis) and the Asian longhorned tick (Haemaphysalis longicornis)may also carry alpha-gal or convey similar risk.

Allergy symptoms sometimes fade in the long-term.

In many cases, sensitization fades over 3–5 years, but each new tick bite can “reset the clock.” Ongoing tick exposure therefore prolongs disease and complicates individual cases.

AGS is not covered by the allergy related labeling laws.

Avoiding allergenic foods is harder than it sounds, because alpha-gal–containing ingredients are not labeled to identify risky ingredients. Gelatin may be listed simply as “gelatin” without identifying the animal source.

Policy proposals to require alpha-gal labeling have been considered, but none have passed. So for now, at least, hidden exposures remain common.

In some cases, AGS can pose a special risk for MC patients.

Note how closely some of the symptoms of AGS resemble the symptoms of MC, so that AGS reactions might be mistaken for an MC flare, in some cases. Specifically:
diarrhea
hives (for those of us who have histamine issues associated with MC)

Be especially mindful of respiratory symptoms (if they are present), since those are usually not associated with MC, and in some cases they can lead to a fatal outcome.

If you suspect that you might have AGS:

• Ask your GP to order alpha-gal–specific IgE lab testing as part of the workup.
• If the diagnosis is positive, strictly avoid mammalian meat, and consider avoiding dairy and gelatin, depending on sensitivity.
• Carry an EpiPen (epinephrine autoinjector) and remember the delayed-reaction risk.

And for those of us who don't have AGS:

It definitely behooves us to take personal protective measures when in tick habitat, especially around bushes, trees, and tall grass. And remember, ticks can jump. Inspect for and remove any ticks promptly. Taking measures to avoid becoming infected with AGS may seem to be bothersome, but minimizing the risk is much less bothersome than avoiding mammalian meat after an allergy develops.

The Bottom line:

AGS has moved from a rare curiosity to a mainstream clinical reality. It's tick-initiated, IgE-mediated, delayed in onset, and potentially fatal, but often remits without new bites. As cases spread north and west in the U.S. and continue to surface globally, when outdoors, everyone should remain vigilant, and do their best to avoid tick bites. If infected, patients should recognize that safety gaps in labeling exist, and be especially careful when buying processed foods.

Reference

1. McKnight, W. (2025, October 01). Alpha-Gal Syndrome, the Meat Allergy, Expands Its Reach. Medscape, Retrieved from https://www.medscape.com/viewarticle/alpha-gal-syndrome-meat-allergy-expands-its-reach-2025a1000qcz