Red meat allergy: Alpha-gal syndrome
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The bottom line
Alpha-gal syndrome is an allergic reaction to a sugar found in mammals. It is transmitted by the lone star tick bite. Onset is 6 hours after ingesting red meat and other alpha-gal substances. Symptoms include hives, vomiting, wheezing, and anaphylaxis. Treatment is avoiding meat and other alpha-gal substances. Reactions are treated with antihistamines and epinephrine auto-injectors.
Prevention Tips
Avoid tick bites.
Avoid wooded areas with high grass.
Wear long pants and long-sleeved shirts.
Use tick repellants such as permethrin on clothing.
Check for ticks when you come inside.
If you have alpha-gal syndrome:
Avoid eating meats such as beef, pork, lamb, venison, and rabbit.
Avoid products derived from meat.
Avoid other sources of alpha-gal that you are sensitive to.
Check for carrageenan in food and medications.
If you have serious allergic reactions, always carry an EpiPen with you.
This Really Happened
A 10-year-old boy experienced urticaria, itchy ears and throat, and vomiting 6 hours after eating a cheeseburger. His symptoms were treated with diphenhydramine at home. He ate a cheeseburger a few weeks later and experienced nausea and urticaria and again was treated with diphenhydramine at home. His family had a lake home in Central Florida, and he had a history of lone star tick bites. An alpha-gal-specific IgE panel was ordered and showed an elevated specific IgE level. The diagnosis was alpha-gal syndrome. He was told not to eat mammalian meat, and an epinephrine auto-injector was prescribed. Follow-up one year later found no recurrent reactions after avoiding meat.
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What is alpha-gal syndrome?
Alpha-gal syndrome is an allergic reaction to red meat and dairy products that can be life-threatening. Alpha-gal is a sugar, galactose-alpha-1,3-galactose, found in mammals such as cows and pigs, but not in people. The immune system reacts to foods from mammals containing this sugar.
How do you get alpha-gal syndrome?
You get alpha-gal syndrome from a tick bite, most often the lone star tick. If the tick bites a mammal and then a person, it transfers the alpha-gal sugar to the person. This causes the immune system to produce IgE antibodies to alpha-gal, which can trigger an allergic reaction when the person later eats red meat or other mammal products.
Foods to avoid
Individuals with alpha-gal syndrome should avoid meat from mammals. Examples include beef, pork, lamb, venison, and rabbit. In some cases, people need to avoid milk and milk products, especially cow’s milk. Other sources of alpha-gal include beef or pork gelatin, lard, tallow, suet, meat broth, meat bouillon, and gravy.
Non-food products to note
Some non-food products contain alpha-gal. For example, the additives, stabilizers, or coatings in some medications such as gelatin, glycerin, and magnesium stearate may contain alpha-gal. People with alpha-gal syndrome may develop a hypersensitivity reaction to the monoclonal antibody cancer drug cetuximab because the drug contains alpha-gal sugar molecules on its surface. This was actually one of the first clues that helped researchers discover alpha-gal syndrome, because severe reactions to cetuximab were occurring more often in regions where lone star tick bites were common.
Alpha-gal syndrome and lab-grown beef
Lab-grown meat is produced from animal muscle cells. Certain allergens are present at lower levels in lab-grown cells. However, a study found a stronger interaction between IgE and alpha-gal in lab-grown cells. This suggests an increased risk of allergic reactions to lab-grown meat in people with alpha-gal syndrome.
Alpha-gal syndrome and carrageenan
Carrageenan is used as an emulsifier (an additive that allows water and oil to mix) in food and in some medications. It is derived from red seaweed. Although it is not from an animal source, it is a commonly reported allergen in people with alpha-gal syndrome.
Signs and symptoms
Allergic reactions are usually delayed 3-6 hours. Alpha-gal syndrome affects skin, gastrointestinal tract, lungs, and the cardiovascular system. Skin reactions include hives, itching, and swelling. Other symptoms include abdominal pain, vomiting, and diarrhea, as well as trouble breathing and wheezing. The most serious reaction is anaphylaxis in which the person has trouble breathing and/or blood pressure drops significantly, resulting in shock.
Is there a test for alpha-gal syndrome?
Yes, there is a test for antibodies that your body has produced in response to alpha-gal.
Can alpha-gal syndrome be cured?
No, alpha-gal syndrome cannot be cured.
How is alpha-gal syndrome treated?
Mild reactions can be treated with antihistamines such as cetirizine (Zyrtec®) or diphenhydramine. More serious reactions require treatment with injectable epinephrine (EpiPen).
Living with alpha-gal syndrome
If you have alpha-gal syndrome, you should stop eating meat from mammals. You should also stop eating or drinking milk and milk products if you cannot tolerate them. You can eat poultry, fish, seafood, eggs, fruits, and vegetables. You should work with a health care professional and/or dietician for counseling about which foods and other products to avoid and what to do if you experience a reaction.
What should you do if you think you are having an alpha-gal reaction?
If you have alpha-gal syndrome and think you are having an alpha-gal reaction, treat it with an antihistamine and/or EpiPen. If this is the first time you are experiencing what you think is an alpha-gal reaction, seek medical attention immediately, especially if you are experiencing more serious symptoms described above.
If someone is having an alpha-gal reaction or if you have a question about alpha-gal syndrome, use the webPOISONCONTROL® online tool to get help, or call your poison center at 1-800-222-1222. Whether online or by phone, expert guidance is always free, confidential, and available 24 hours a day.
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