A recent study published in Morbidity and Mortality Weekly Report revealed a significant finding: in five states known for high rates of alpha-gal syndrome (AGS), almost a quarter of adults tested positive for antibodies linked to the condition. This suggests that the trigger for AGS might be far more widespread than previously understood.
Alpha-gal syndrome is an allergic reaction caused by exposure to alpha-gal, a sugar present in red meat, dairy, and other animal byproducts. Exposure can lead to symptoms ranging from hives and swelling to respiratory distress and, in rare cases, severe reactions.
In most US instances, the syndrome is associated with bites from the lone star tick. This tick carries alpha-gal in its saliva, and its bite can prompt the human immune system to produce alpha-gal-specific immunoglobulin E (IgE) antibodies.
To assess the prevalence of these antibodies independent of actual symptoms, researchers from the Centers for Disease Control and Prevention analyzed blood donor samples from 10 states between November 2024 and April 2025. The selection included five states with historically high occurrences of alpha-gal antibodies – Arkansas, Kentucky, Missouri, Tennessee, and Virginia – alongside five states with lower reported cases.
Arkansas Shows Highest Antibody Levels
Arkansas exhibited the highest estimated prevalence of alpha-gal IgE antibodies, with 31.2% of adults testing positive. Missouri followed at 26.0%, while Virginia, Kentucky, and Tennessee all reported over 21%. Collectively, these five states showed an estimated prevalence of 24.0%, a figure considerably higher than the estimated 450,000 US adults (0.14% of the population) diagnosed with AGS.
In contrast, states like New Mexico (1.9%) and Washington (1.1%), where lone star ticks are not found, displayed much lower antibody rates.
The study’s authors caution that relying solely on positive alpha-gal IgE test results without corroborating clinical symptoms could lead to overdiagnosis and unnecessary dietary limitations.
The research also indicated differences in antibody prevalence based on demographics. Individuals aged 16 to 34 had a 60% lower seroprevalence compared to those aged 55 to 64. Men were also more likely to test positive than women, and Hispanic individuals showed lower seroprevalence than non-Hispanic individuals. Additionally, higher population density within a county was associated with a decreased probability of testing positive for alpha-gal IgE antibodies.
A Positive Test Doesn’t Always Mean a Diagnosis
The researchers emphasize that a positive alpha-gal IgE test result alone does not confirm a diagnosis of AGS. They recommend that such testing be reserved for patients presenting with symptoms consistent with the syndrome.
"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 study authors stated.
Ultimately, the researchers suggest that broad serological surveys can be valuable tools for identifying regions where AGS may be underdiagnosed, guiding efforts in tick bite prevention, improving clinician education, and enhancing disease surveillance.