A new study led by researchers from the University of North Carolina and the Centers for Disease Control and Prevention (CDC) has found that nearly one in four people aged 16 and older in five US states with historically high rates of alpha-gal syndrome (AGS) have antibodies to alpha-gal. By analyzing 3,000 blood donor samples collected from 10 states, researchers uncovered a surprisingly high rate of exposure to the allergen associated with AGS—commonly known as the tick-bite-related red meat allergy. The findings highlight the growing public health importance of this emerging condition while also underscoring that many people who develop these antibodies never go on to develop the allergy itself.
Alpha-gal syndrome is a serious and potentially life-threatening allergic condition triggered by exposure to galactose-α-1,3-galactose (alpha-gal), a sugar molecule naturally found in red meat and other mammalian products. Humans do not produce alpha-gal themselves. In the United States, the condition most commonly develops after the bite of a lone star tick, whose saliva can trigger the immune system to produce IgE antibodies against the sugar. In susceptible individuals, those antibodies can later cause allergic reactions after eating mammalian meat or being exposed to certain other mammalian-derived products.
The study revealed striking geographic differences in alpha-gal antibody prevalence, with the overall pattern closely matching regions where alpha-gal syndrome has been reported most frequently. Arkansas recorded the highest estimated antibody prevalence at 31.2%, followed by Missouri at 26.0%. Across the five states with the highest prevalence—Arkansas, Kentucky, Missouri, Tennessee, and Virginia—an estimated 24.0% of people aged 16 and older had alpha-gal antibodies. By comparison, Washington State had the lowest estimated prevalence at just 1.1%.
Researchers also identified several demographic trends. Men were significantly more likely than women to test positive for alpha-gal antibodies. Adults between the ages of 16 and 34 were significantly less likely to test positive than those aged 55 to 64, suggesting that cumulative exposure to tick bites over time may contribute to higher rates of sensitization. Positive samples were found in urban, suburban, and rural communities alike, although antibody prevalence generally declined as county population density increased, reflecting greater opportunities for tick exposure in less densely populated areas.
Importantly, the researchers emphasized that testing positive for alpha-gal antibodies does not necessarily mean someone has alpha-gal syndrome. A positive blood test indicates that the immune system has become sensitized to alpha-gal, but many people with detectable antibodies never develop symptoms after eating red meat or other mammalian products. For that reason, current medical guidance recommends testing only people whose symptoms are consistent with alpha-gal syndrome, since widespread testing of healthy individuals could lead to unnecessary dietary restrictions and confusion.
Lead author Dr Eleanor Saunders said the findings could help public health officials better understand where alpha-gal exposure is occurring and direct resources where they are needed most.
“Blood donor seroprevalence data provide a valuable picture of where alpha-gal exposure is occurring. These findings support a geographically focused approach to surveillance, prevention, and provider education in communities at greatest risk.”
The researchers say these data represent an important step toward understanding how widespread alpha-gal sensitization has become across the United States. Future studies will help determine what proportion of people who develop alpha-gal antibodies ultimately go on to develop clinically significant alpha-gal syndrome and why only some sensitized individuals become symptomatic.
The authors also caution that the findings have limitations. The study analyzed blood donors rather than a random sample of the US population, and blood donors tend to differ from the general public in several ways. The sample was also predominantly White, and blood donations were not evenly distributed within every state. Although the researchers adjusted the results to better reflect each state’s age and sex distribution, the reported estimates should still be viewed as approximations rather than precise population-wide rates.
Ticks carrying alpha-gal may already be in your yard. Learn how to protect yourself:
