Alpha-gal syndrome (AGS) is a serious, potentially life-threatening, allergic reaction to a sugar molecule found in red meat, including beef, pork, buffalo, goat, venison, or lamb, and in meat-related products. Experts suggest that AGS is triggered by the bite of certain types of ticks, such as the lone star tick in the U.S. Symptoms occur in individuals who have been bitten by a tick and in ensuing days eat meat or are exposed to other meat-related products containing alpha-gal, such as dairy, gelatin and gravies.

Identifying alpha-gal allergy is complicated by the fact that there are many mammalian-derived products and sources in such everyday items as gummy bears, cheese, medication-related capsules made from gelatin, medications (for example, heparin and thyroid hormone), certain vaccines, and unlabeled “natural flavorings” in many foods.

Incidence of Alpha-gal
Incidence of Alpha-gal (as reported by patients, 2017)
(Source: Zee Maps)

Adult female lone star tick
Adult female lone star tick
Source: Northeast Regional Center for Excellence in Vector-borne Diseases

Which Tick Is the Primary Vector?

In the United States, lone star tick bites are associated with experiencing AGS. Lone star ticks are found from Texas to Maine on the east coast and in the Midwest and upper Midwest as far north as the Canadian border (see the map). They thrive in wooded areas with thick underbrush and along the edges of meadows and streams. They are aggressive biters. The potential for other kinds of ticks to cause AGS is being studied, since different tick species have been responsible for AGS reactions in other countries.

Who Is Most at Risk?

Alpha-gal affects both adults and children. It can occur suddenly for the first time in people who have eaten red meat their entire lives. More than a third of patients report having 15 or more reactions prior to diagnosis. One in four still react at least once a month and 39% have visited the emergency department due to a reaction. Referred to by experts as a “life-changing” diagnosis, the impact of AGS can restrict food options to vegetables, chicken, fish and other seafood.


Symptoms usually appear 2–6 hours after eating meat, dairy products or other items that carry the Alpha-gal molecule.

Alpha-gal reactions may include:

  • Hives or itchy rash
  • Nausea or vomiting
  • Heartburn or indigestion
  • Diarrhea
  • Cough, shortness of breath, or difficulty breathing
  • Drop in blood pressure
  • Swelling of the lips, throat, tongue, or eye lids
  • Dizziness or faintness
  • Severe stomach pain

Researchers have also noted a wide range of previously undocumented symptoms, including those relating to the cardiovascular system (heart) (41%), emotional issues (35%), the nervous system (22%) and motor (body movement) (22%) systems.

More severe reactions include a potentially-deadly allergic reaction that restricts breathing (anaphylaxis). Patients with anaphylaxis (lips, throat or tongue swelling), and/or a severe rash along with nausea and vomiting and light-headedness, should seek immediate medical care.


AGS symptoms occur after people eat red meat or are exposed to other foods that contain the Alpha-gal molecule, including milk and milk products. Most of the individuals who experience AGS symptoms have had no previous food allergies. Researchers now believe that some who experience frequent, unexplained anaphylactic reactions — but test negative for other food-related allergies — may be affected by AGS.


There's no treatment for AGS other than avoiding additional tick bites and never eating red meat and other products made from mammals. This includes meat and products from cows, horses, buffalo, deer, goats, sheep and pigs. AGS can also affect the person’s use of certain cosmetics, pharmaceuticals, and medical devices. Mammal-derived materials in foods, medications, personal care products, and valves used to help repair human hearts should be avoided. Just 8% of patients report having had their AGS reactions resolve over time.


Prevention of tick bites is important in helping to reduce the chances of developing AGS and in recovering from it should it occur. While outdoors, avoid wooded areas with dense shrubs and leaf litter. Lone star ticks are most active from March through September and whenever winter temperatures are above freezing. Dress appropriately and use repellents with active ingredients, such as DEET, that are registered by the EPA for efficacy against ticks. The American Academy of Pediatrics and the Centers for Disease Control and Prevention note that repellent products containing up to 30% DEET are appropriate for children over two months of age. For more information, please visit our prevention page.