What happened
On July 2, 2026, the CDC published a study in its journal Morbidity and Mortality Weekly Report (MMWR) on alpha-gal antibodies in blood donors. Alpha-gal syndrome (AGS) is a tick-related allergy to red meat and other products made from mammals. In the United States, it is most often linked to bites from the lone star tick.
Researchers from the CDC, the University of North Carolina at Chapel Hill, the American Red Cross and blood-testing partners tested 3,000 leftover donor blood samples, 300 from each of 10 states. They looked for alpha-gal IgE, the type of antibody involved in this allergy. The samples were collected between November 2024 and April 2025.
- Estimated share of adults with alpha-gal antibodies, highest to lowest: Arkansas 31.2%, Missouri 26.0%, Virginia 22.8%, Kentucky 22.7%, Tennessee 21.5%, Maine 10.6%, South Carolina 5.5%, Minnesota 5.4%, New Mexico 1.9%, Washington 1.1%.
- Across the five highest states combined, the estimate was 24.0%, or nearly 1 in 4 adults.
- Antibodies were more common in men than women, in people aged 55 to 64 than in people under 35, and in less densely populated counties.
What it means for you
- Tick bites leave a mark on the immune system more often than we thought, at least in lone star tick country. The CDC has estimated that as many as 450,000 people in the U.S. may be affected by AGS, and this study suggests far more people carry the antibody.
- Know the symptoms. According to the CDC, AGS reactions usually start about 2 to 6 hours after eating red meat or dairy. They can include hives or itching, nausea or vomiting, severe stomach pain, diarrhea, trouble breathing, swelling of the lips or throat, and dizziness. Because the reaction is delayed, many people do not connect it to the meal.
- If that sounds familiar, talk to a clinician. The CDC says AGS is diagnosed with a physical exam, a detailed history and a blood test, and is best managed by an allergist or other provider. Our alpha-gal syndrome guide explains more.
A severe allergic reaction (anaphylaxis) is an emergency. If you have trouble breathing, throat or tongue swelling, or feel faint, call 911 or get emergency care right away. A past mild reaction does not mean the next one will be mild.
What it does not mean
- It does not mean 1 in 4 people have alpha-gal syndrome. Having the antibody is not the same as having the allergy. The authors stress that only a small minority of people who test positive actually have AGS.
- It is not a reason to get tested if you feel fine. The authors advise that clinicians test only people with symptoms that fit AGS. Testing people without symptoms could lead to a wrong label and needless diet restrictions.
- It is not a reason to cut out meat on your own. Any food changes should follow a diagnosis made with your clinician, not an antibody number alone.
- The numbers are estimates, not a census. Blood donors tend to be healthier and are not a perfect mirror of the general population, and sampling within each state was uneven. The authors say this could push the estimates up or down.
What happens next
The authors suggest that a more specific test, and possibly a higher cut-off for calling a result positive, may be needed to tell true AGS apart from harmless antibodies. They also say high antibody levels in an area can act as an early warning for places where AGS may be underdiagnosed, which can guide tick-bite prevention and doctor education.
The best protection is still preventing tick bites. See our tick-bite prevention guide, and if you have been diagnosed, our page on food and Lyme disease and the Live well with Lyme step on our hub.