Alpha-gal Immunoglobulin E Seroprevalence Among Blood Donors — 10 States, 2024–2025

Alpha-gal syndrome (AGS) is an emerging, noninfectious tickborne disease characterized by an allergic reaction to galactose-α-1,3-galactose (alpha-gal), an oligosaccharide found in red (mammalian) meat and other mammalian products such as dairy and gelatin. As of 2022, AGS was estimated to affect up to 450,000 persons in the United States (1). Anaphylactic AGS reactions can be fatal, and AGS allergic reactions encompass a range of symptoms including urticaria, angioedema, wheezing, and gastrointestinal distress. AGS is primarily managed through an avoidance diet. The U.S. geographic distribution of AGS is closely associated with the range of the lone star tick (Amblyomma americanum); bites from this tick introduce alpha-gal through its saliva, which can trigger the allergy. Diagnosis of AGS requires both the presence of clinically compatible symptoms and the detection of serologic immunoglobulin E (IgE) antibodies against alpha-gal. Persons can have alpha-gal-specific IgE antibodies without clinical symptoms. The proportion of persons in the United States who are seropositive for alpha-gal IgE is unknown. To better understand the distribution and seroprevalence of alpha-gal IgE among U.S. adults, 3,000 serum samples collected during November 2024-April 2025 from blood donors living in 10 states were tested for the presence of alpha-gal IgE antibodies. States previously reported to have high numbers of suspected AGS cases were found to have correspondingly high seroprevalences. Among the 10 states, the highest estimated seroprevalences among persons aged ≥16 years were detected in Arkansas (31.2%) and Missouri (26.0%). These findings can guide the development of surveillance systems for AGS and help identify regions at increased risk.