In five states with high rates of alpha-gal syndrome (AGS), nearly one in four adults test positive for antibodies associated with the condition, according to a study published last week in Morbidity and Mortality Weekly Report. The findings suggest that the presence of the molecule that triggers AGS may be far more common than the syndrome itself.

AGS is an allergy triggered by exposure to galactose-α-1,3-galactose, or alpha-gal, a sugar found in mammalian (red) meat, dairy products, and mammalian-derived byproducts like gelatin. People with AGS can experience hives, swelling, wheezing, or gastrointestinal symptoms or, rarely, they might die when they consume these foods. 

Most US cases are linked to bites from lone star ticks (Amblyomma americanum). Alpha-gal is found naturally in lone star ticks’ saliva and, when it is transferred to humans through a bite, can induce the production of alpha-gal–specific immunoglobulin E (IgE) antibodies. 

To better understand how common alpha-gal antibodies are regardless of a person’s clinical symptoms, a team led by Centers for Disease Control and Prevention researchers tested 3,000 residual blood donor samples collected from 10 states from November 2024 to April 2025. The states included five with historically high alpha-gal seroprevalence—Arkansas, Kentucky, Missouri, Tennessee, and Virginia—as well as five states with lower disease activity.

The highest estimated prevalence of alpha-gal IgE antibodies was found in Arkansas, where 31.2% of adults were estimated to be seropositive. Missouri followed, at 26.0%, with Virginia, Kentucky, and Tennessee all above 21%. Together, these five states had an estimated seroprevalence of 24.0%—a rate that far exceeds the 450,000 US adults estimated to have AGS (0.14% of the population). 

Prevalence was much lower in New Mexico (1.9%) and Washington state (1.1%), both states with no known lone star tick populations. 

Reliance on positive alpha-gal IgE test results without considering whether patients also have clinical signs and symptoms of AGS might result in overdiagnosis and unnecessary dietary restrictions.

Seroprevalence was 60% lower among people aged 16 to 34 years old than among adults 55 to 64 (odds ratio [OR], 0.40), according to the findings. It was also higher among men than in women (OR, 1.61). Seroprevalence was lower among Hispanic people than among non-Hispanic people (OR, 0.43). 

Per county, population density was inversely associated with seropositivity. For every tenfold increase in population density in a specific county, the probability that a resident would test positive for alpha-gal IgE antibodies decreased 29.5%. 

A positive alpha-gal IgE test does not necessarily mean a person has AGS, say the researchers, who recommend that testing be reserved for patients with clinically compatible symptoms. 

“Reliance on positive alpha-gal IgE test results without considering whether patients also have clinical signs and symptoms of AGS might result in overdiagnosis and unnecessary dietary restrictions,” the researchers write.

The authors conclude that serosurveys may help identify areas where AGS is underrecognized and could guide future surveillance, tick-bite prevention efforts, and clinician education.