Chapel Hill, NC, July 18: A new study examining blood donor samples from across the U.S. has found that nearly one in four adults in states with the highest rates of alpha-gal syndrome has positive antibodies to the allergen associated with the condition, underscoring the growing public health impact of this emerging tick-borne disease.
Alpha-gal syndrome is an allergic condition triggered by exposure to galactose-α-1,3-galactose, a sugar molecule found in red meat and other mammalian products. In the U.S., the condition is commonly associated with bites from the lone star tick. Symptoms can range from hives and gastrointestinal distress to severe, potentially life-threatening allergic reactions.
First author Eleanor Saunders, MD, MPH, in collaboration with Scott Commins, MD, PhD, a leading expert on alpha-gal syndrome with the Institute for Global Health and Infectious Diseases at the UNC School of Medicine, published the study Alpha-gal Immunoglobulin E Seroprevalence Among Blood Donors – 10 States, 2024–2025. Dr. Commins is the William J. Yount Distinguished Professor of Medicine and UNC Health’s Associate Chief for Allergy and Immunology.
Designing the Study
The Commins lab tested 3,000 blood donor samples collected between November 2024 and April 2025 from residents of 10 states. The analysis revealed that the estimated prevalence of alpha-gal immunoglobulin E antibodies – or proportion of the population “sensitized” to alpha-gal – was highest in states where lone star ticks are well established.
The study found significant variation in alpha-gal IgE seroprevalence across the U.S. Arkansas had the highest estimated seroprevalence at 31.2%, followed by Missouri at 26.0%. Across the five states with the highest prevalence – Arkansas, Kentucky, Missouri, Tennessee, and Virginia – the combined estimated seroprevalence was 24.0%, meaning nearly one in four adults would test positive for alpha-gal antibodies. In contrast, Washington State had the lowest estimated seroprevalence at just 1.1%. Researchers also identified positive test results in urban, suburban, and rural communities, although prevalence generally declined as population density increased.
Despite the high prevalence of antibodies, researchers stress that a positive alpha-gal IgE test does not necessarily mean a person has alpha-gal syndrome.
“Many individuals may be sensitized to alpha-gal and have detectable antibodies without experiencing any symptoms,” explained Saunders, assistant professor of medicine in infectious diseases. “Diagnosis of AGS requires both a compatible clinical history and laboratory evidence.”
The findings reinforce concerns that relying solely on blood test results could lead to overdiagnosis and unnecessary dietary restrictions. Current public health guidance recommends alpha-gal testing only for patients with symptoms consistent with AGS, such as delayed allergic reactions after consuming red meat or other mammalian products.
Alpha-gal syndrome was estimated to affect up to 450,000 people in the U.S. in 2022, but this study suggests that many more individuals may have been exposed to alpha-gal and developed antibodies without developing the syndrome itself. The primary known exposure that can result in both allergy and the much more common asymptomatic sensitization is a tick bite.
Researchers also identified several demographic trends associated with alpha-gal IgE seropositivity. Rates were higher among adults ages 55 to 64 compared with younger age groups, and men were more likely than women to test positive for alpha-gal antibodies. In addition, residents of less densely populated counties had higher rates of seropositivity, likely reflecting increased opportunities for tick exposure in rural and semi-rural areas. These findings suggest that age, sex, and geographic location may all play a role in the likelihood of developing sensitization to alpha-gal.
The geographic distribution of alpha-gal antibodies closely mirrored areas where suspected AGS cases have previously been reported, providing valuable information for public health officials and clinicians.
Implications for Public Health
Authors say the findings can help strengthen surveillance efforts, improve awareness among healthcare providers, and guide targeted tick-bite prevention strategies in high-risk regions.
As more states begin reporting AGS cases and surveillance expands, researchers hope additional data will help determine what proportion of people with alpha-gal antibodies eventually develop clinical disease.
The authors conclude that public health investigations should continue to combine laboratory testing with clinical evaluation, and that more specific diagnostic tools may be needed to improve disease surveillance and reduce unnecessary diagnoses.
“Blood donor seroprevalence data provide a valuable picture of where alpha-gal exposure is occurring,” said Saunders. “These findings support a geographically focused approach to surveillance, prevention, and provider education in communities at greatest risk.”