You might not have seen a case of it yet, but odds are increasing that a patient with an emerging meat allergy could present to your clinic.

Alpha-gal syndrome (AGS), the tick-borne allergy to animal products, is on the move north and west from the Mid-Atlantic and Southern states where it has been most observed.

Researchers led by immunologist Thomas Platts-Mills, MD, at the University of Virginia in Charlottesville, began publishing their findings on the relationship between tick bites and meat allergies in the early 2000s.

“In 2009, we published our first article about it,” recalled Scott Commins, MD, PhD, a leading expert on AGS. “We just reported on 24 people, that was it. We thought it was kind of interesting, but I don’t think any of us thought in 2025 we’d still be having conversations about it,” he told Medscape Medical News in an interview.

Commins is the William J. Yount Distinguished Professor of Medicine and Associate Chief for Allergy & Immunology at The University of North Carolina at Chapel Hill.

“In the first 24 people, we had five from Missouri,” Commins said. “What we have seen, though, is that there is expansion into the Great Lakes and Eastern Nebraska.”

Tick Spit

Alpha-gal is the oligosaccharide galactose-alpha-1,3-galactose, a sugar found in most mammals, but not in primates. It is also found in tick spit, specifically the spit of the lone star tick (Amblyomma americanum).

A person who gets a lone star tick bite is automatically at risk for the alpha-gal allergy, according to Commins.

Not all tick-bitten persons will develop the allergy, and not all persons who are affected by the allergy will have the same severity of symptoms, he said. What makes a person more susceptible, however, is still unknown.

Alpha-gal allergy is immunoglobulin E (IgE) mediated, causing the sufferer to develop an inability to tolerate meat and other animal products such as dairy and gelatin, two ingredients that appear in many prepared foods.

If alpha-gal is in all mammals, why don’t people become allergic to meat after, say, being bitten by a cat?

“A cat is not injecting you with anything,” Shahid Kamrim, PhD, a professor of microbiology and cellular biology at The University of Southern Mississippi, Hattiesburg, Mississippi, told Medscape Medical News in an interview. Karim studies tick vectors.

“The tick’s saliva has a protein that is triggering this whole cascade of reactions where we have an allergic response,” Karim said.

Presentation

The symptoms of AGS include severe urticaria, intestinal distress, sudden drop in blood pressure, and other presentations. These only appear after a person with a tick bite has eaten meat or related product, and even then, there is a delay of at least several hours before symptoms present, according to Commins.

The CDC, which published its first guide to the emergent condition earlier this year, warns AGS could be deadly because of the possibility of severe anaphylaxis.

Respiratory complaints are less common in persons with AGS than with other allergies, according to Commins, but asphyxiation has been reported in several alpha-gal-related deaths. Still, in addition to hives and diarrhea, cardiovascular symptoms are more prevalent than respiratory ones, he said.

“We call it cardiovascular collapse. Things like chest pain and low blood pressure,” Commins said.

AGS will eventually resolve itself, typically within 3-5 years. “But if you get another tick bite in that time period, the clock resets itself,” Commins said.

Spike in Cases

Karim said that AGS cases have “exploded” in the last 10-15 years, but that until recently, these cases were going underreported.

“People were getting sick, but they didn’t know what was causing the reaction,” Karim said. “There is more awareness now.”

Since 2009, when Commins and colleagues reported on just 24 cases of AGS, the number of reported cases has risen to 450,000, according to CDC. But why this allergy seems to be increasing — especially if the sugar has been present in mammalian (but not primate) biology for millions of years, and, given the chance, ticks have always bitten humans — is a matter of debate.

In places where the lone star tick is more prevalent, such as Virginia and the Carolinas, there has been a rise in awareness of AGS, according to Commins, but there may be little to no awareness of it in places where the tick is not found.

More awareness, more diagnoses. But according to Karim “Tick bites are more prevalent than they used to be.”

Why is that? “There is more contact with deer. The white-tailed deer is the primary vector for lone star ticks,” said Commins.

A modeling study published earlier this year in PLOS Climate predicted that, “As low-intensity development has continued throughout the US, humans have encroached on tick habitat, while tick ranges have expanded due to climate change.”

The study also found that human and white-tailed deer habitats are increasingly overlapping, stating that, “edge habitat and fragmented forest near a person’s residence may be an important driver of AGS risk.”

Karim added that it’s possible that it’s not just the lone star tick carrying the AGS-causing saliva. He referenced a study published earlier this year in the CDC’s Emerging Infectious Diseases, which asserts that the deer tick (Ixodes scapularis) also carries the alpha-gal allergen.

AGS is reported globally, including in places where the lone star tick does not live. “There are 80-90 species that have been implicated in alpha-gal syndrome across the world,” Karim said, listing several from places like Brazil, Argentina, Australia, and parts of Africa. In Europe, the blacklegged tick, Ixodes ricinus, has been shown to cause AGS there.

Further, Karim said the Asian longhorned tick (Haemaphysalis longicornis), which officially found its way to the US in 2017, and may have been here as early as 2013, is another threat to humans. Whether that threat is AGS has yet to be determined in the US, but it has been confirmed in Japan.

Current Research

Commins said some current AGS research, including his own, is centered on determining who is most at risk for the syndrome, and whether the risk is inherent to the host or the tick.

“Is there a genetic component or is it just really random?” It may matter more how long the tick is attached and where it is attached, like near a lymph node, Commins said.

No treatment has been identified to date, but Commins said there have been some legislative efforts to add galactose-alpha-1,3-galactose to food labels, but nothing has passed so far.

“These mammal ingredients now are totally hidden,” Commins said. “They can be called various things. Like gelatin can be called just gelatin, but you don’t know if it comes from a fish, a plant, or a cow. So that’s potentially a policy thing coming, but we don’t know.”

Commins reported being a consultant to or on advisory boards for Genentech (IgE mechanisms in allergic diseases, urticaria) and Regeneron (Th2- and IgE-related mechanisms). Karim had no disclosures.