What is Alpha-gal Syndrome?

Alpha-gal syndrome (AGS) is a serious, potentially life-threatening allergic reaction triggered by a sugar molecule called galactose-α-1,3-galactose (alpha-gal). The condition develops after a person is bitten by a lone star tick, which transmits the molecule to the bloodstream. Once sensitized, the immune system may react violently to any product derived from mammals — including beef, pork, lamb, dairy, and gelatin.

Symptoms

  • Hives, itching, or rash on the skin
  • Swelling of the lips, tongue, or throat
  • Shortness of breath or wheezing
  • Stomach pain, nausea, vomiting, or diarrhea
  • Dizziness or fainting; in severe cases, anaphylaxis

Reactions typically appear 3 to 6 hours after eating, which can make the cause difficult to recognize.

Free Public Health Briefing
Health professionals have prepared an open educational briefing for the public. It explains the warning signs, at-risk regions, and the simple defensive steps American families can take starting today. Watch the briefing above.

Where the Risk Is Highest

The lone star tick — identifiable by the single white spot on the female's back — was once limited to the southeastern United States. It is now established in 45 states, with rapid northward expansion into New England and westward into the Great Plains, driven by warming winters and rising deer populations.

What You Can Do

  • Avoid wooded and brushy areas with high grass and leaf litter.
  • Use EPA-registered insect repellents containing DEET, picaridin, or IR3535.
  • Treat clothing and gear with products containing 0.5% permethrin.
  • Conduct a full-body tick check after outdoor activity.
  • Talk to your healthcare provider if you experience unexplained allergic reactions after meals.

For additional clinical guidance and full case data, see the CDC's vector-borne diseases resources.