Alpha-gal syndrome (AGS) is an allergic condition where people develop an allergy to a sugar molecule called galactose-alpha-1,3-galactose (alpha-gal). This sugar is found in the tissues of most mammals except humans and other primates. People with AGS experience allergic reactions to red meat such as beef, pork, lamb, and other mammalian meats, as well as some mammalian products like dairy and gelatin. AGS typically develops after a tick bite, most commonly from the lone star tick in the United States. When the tick bites, it can pass alpha-gal from its saliva into the person's bloodstream, prompting their immune system to produce antibodies against alpha-gal. When the person later consumes mammalian meat products containing alpha-gal, these antibodies trigger allergic reactions. The allergy symptoms usually appear 2 to 6 hours after eating red meat and can range from mild to severe, including:
- Rash, hives, and itching,
- Swelling of lips, face, throat, or eyelids,
- Wheezing or shortness of breath,
- Stomach pain, nausea, vomiting, and diarrhea,
- In severe cases, anaphylaxis which requires emergency medical attention.
People with AGS need to avoid eating mammalian meats and products that contain alpha-gal to prevent allergic reactions. Interestingly, they can still eat non-mammalian meats such as chicken, turkey, and fish safely. Over time, some people may lose their sensitivity if they avoid tick bites and exposure to alpha-gal-containing products. In summary, alpha-gal syndrome is a tick- bite–induced allergy to a carbohydrate found in mammalian meat and products, causing delayed allergic reactions that can be life-threatening.
