Alpha-gal syndrome (AGS) is a recently identified type of food allergy red meat and other animal-derived products. In the United States, the condition is most often caused by a bite from Lone Star tick, known in Italy as the lone star tick. The bite transmits a sugar molecule called alpha-gal into the person's body. In some people, this triggers an immune system reaction that later produces mild to severe allergic reactions to red meat, such as beef, pork or lamb, or other mammalian products.
The lone star tick is predominantly found in the southeastern United States, and most cases of alpha-gal syndrome occur in this region, but some have also been diagnosed in Europe, Australia, and Asia.
A bite from this tick, which is easily identified by the white spot on its back if it is a female, can cause a lifelong adverse reaction to eating red meat. When the tick feeds on some mammals, such as mice, rabbits, or deer, it will ingest alpha-gal sugars. Subsequently, when the tick bites a person, it injects alpha-gal sugars into the human host via saliva.
Since humans do not have alpha-gal in their bodies unlike many other mammals, the human immune system recognizes alpha-gal as a foreign substance and then activates a response, including the development of antibodies. It is for this reason that the bite site often becomes red, swollen and puriginous.
The problem stems from the fact that red meat is also rich in alpha-gal sugars. Therefore, if a person bitten by the lone star tick eats red meat, his or her immune system recognizes the alpha-gal in the meat as a foreign substance. As a result, the body activates an immune response that is often much more severe than the initial response to the tick bite.
Alpha-gal allergy to red meat can lead to rashes, hives, itching, swelling, shortness of breath, headache, abdominal pain, diarrhea, and vomiting. In severe cases, a person can suffer from anaphylaxis, a potentially fatal allergic reaction.
Alpha-gal (galactose-α-1,3-galactose) is a sugar molecule found in most mammals, whereas it is not found in fish, reptiles, birds, or people. The molecule may also be present in the meat of animals that produce it (pork, beef, rabbit, lamb, deer, etc.) and in animal-derived products (including gelatin, cow's milk, and dairy products).
Alpha-gal syndrome (AGS) is a serious and potentially life-threatening allergic reaction. It should be noted well that unlike other syndromes caused by tick bite, AGS is not caused by infection: the symptoms of AGS occur after people eat red meat or are exposed to other products containing alpha-gal.
The reactions of AGS may include:
Symptoms commonly appear 2-6 hours after eating meat or dairy products, or after exposureto products containing alpha-gal (e.g., gelatin-coated drugs).
AgS reactions can differ from person to person. They can range from mild to severe or even life-threatening. In case of anaphylaxis (a potentially life-threatening reaction involving multiple organ systems), the person may need urgent medical attention.
AGS is diagnosed by an allergist or other specialist through a detailed patient history, a physical examination, and a blood test that looks for specific antibodies (proteins produced by the immune system) to alpha-gal.
Preventing tick bites is important and can reduce the chances of developing AGS.
Before going outdoors:
After you return from outdoor activity:
Sources: CDC, Mayo Clinic