Alpha-gal syndrome is a recently identified type of food allergy to red meat. In the United States, the condition most often begins when a Lone Star tick bite transmits a sugar molecule called alpha-gal into the body. In some people, this triggers an immune system reaction that later produces mild to severe allergic reactions when they eat red meat.
The Lone Star tick is found predominantly in the southeastern United States, and most cases of alpha-gal syndrome occur in this region. The condition appears to be spreading farther north and west, however, as deer carry the Lone Star tick to new parts of the United States. Alpha-gal syndrome also has been diagnosed in Europe, Australia, and Asia, where other types of ticks carry alpha-gal molecules.
Researchers now believe that some people who have frequent, unexplained anaphylactic reactions — and who test negative for other food allergies — may be affected by alpha-gal syndrome. There's no treatment other than avoiding red meat.
Avoiding tick bites is the key to prevention. Protect against tick bites by wearing long pants and long-sleeved shirts and using insect repellents when you're in wooded, grassy areas. Do a thorough, full-body tick check after spending time outside.
Signs and symptoms of an alpha-gal allergic reaction are often delayed compared with other food allergies. Most reactions to common food allergens — peanuts or shellfish, for example — happen within minutes of exposure. In alpha-gal syndrome, signs and symptoms typically don't appear for three to six hours after eating red meat.
Signs and symptoms of alpha-gal syndrome may include:
- Hives, itching, or itchy, scaly skin (eczema)
- Swelling of the lips, face, tongue and throat, or other body parts
- Wheezing or shortness of breath
- A runny nose
- Abdominal pain, diarrhea, nausea or vomiting
- Sneezing
- Headaches
- Anaphylaxis, a severe, potentially deadly allergic reaction that restricts breathing
Doctors think the time delay between eating red meat and developing an allergic reaction is one reason the condition was overlooked until recently: A possible connection between a T-bone steak with dinner and hives at midnight was far from obvious.
Most people who develop alpha-gal syndrome in the U.S. develop the condition when a Lone Star tick bites them. Bites from other types of ticks can lead to the condition in Europe, Australia and Asia.
Tick bites
Ticks that cause alpha-gal syndrome are believed to carry alpha-gal molecules from the blood of the animals they commonly bite, such as cows and sheep. When a carrier tick bites a human, the tick injects alpha-gal into the person's body.
For unknown reasons, some people have such a strong immune response to these molecules that they can no longer eat red meat without a mild to severe allergic reaction. People who are exposed to many tick bites over time may develop more-severe symptoms.
The cancer drug, cetuximab
People with antibodies related to alpha-gal syndrome can have allergic reactions to the cancer drug cetuximab (Erbitux). Cetuximab-induced cases of this condition are most common in regions with a high population of Lone Star ticks, suggesting a possible link between Lone Star tick bites and an increased vulnerability to alpha-gal syndrome. More research is needed to understand the connection between ticks that carry alpha-gal in certain regions and cases of alpha-gal syndrome that don't seem directly linked to tick bites.
Researchers think the hallmark time-delayed reaction of alpha-gal syndrome is due to the alpha-gal molecules taking longer than other allergens to be digested and enter your circulatory system.
Doctors don't yet know why some people develop alpha-gal syndrome after exposure and others don't. The condition mostly occurs in the southeastern United States and parts of New York, New Jersey and New England. You're at increased risk if you live or spend time in these regions and:
- Spend a lot of time outdoors
- Have received multiple Lone Star tick bites
- Have a mast cell abnormality such as indolent systemic mastocytosis
In the past 20 to 30 years, the Lone Star tick has been found in large numbers as far north as Maine and as far west as central Texas and Oklahoma in the United States.
Alpha-gal syndrome can also occur in other parts of the world such as Europe, Australia and parts of Asia, where bites from certain types of ticks also appear to increase your risk of the condition.
Alpha-gal syndrome can cause food-induced anaphylaxis, a medical emergency that requires treatment with an epinephrine (adrenaline) injector (EpiPen, Auvi-Q, others) and a trip to the emergency room.
Anaphylaxis signs and symptoms can include:
- Constriction of airways
- Swelling of the throat that makes it difficult to breathe
- A severe drop in blood pressure (shock)
- Rapid pulse
- Dizziness, lightheadedness or loss of consciousness
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