While rare, some people experience recurrent episodes of anaphylaxis — a life-threatening allergic reaction that causes symptoms such as the constriction of airways and a dangerous drop in blood pressure — for which the triggers are never identified. Recently, researchers at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, found that some patients’ seemingly inexplicable anaphylaxis was actually caused by an uncommon allergy to a molecule found naturally in red meat. They note that the allergy, which is linked to a history of a specific type of tick bite, may be difficult for patients and health care teams to identify.

As the researchers describe in their article published in Allergy, six of the 70 study participants evaluated for unexplained frequent anaphylaxis tested positive for an allergy to galactose-α-1,3-galactose, or alpha-gal, a sugar molecule found in beef, pork, lamb and other red meats. The six adult male participants all had IgE antibodies — immune proteins associated with allergy — to alpha-gal in their blood. After implementing diets free of red meat, none of them experienced anaphylaxis in the 18 months to 3 years during which they were followed.

While the prevalence of allergy to alpha-gal, or “alpha-gal syndrome” is not known, researchers have observed that it occurs mostly in people living in the Southeast region of the United States and certain areas of New York, New Jersey and New England. This distribution may occur because most people with an allergy to alpha-gal, including all six participants evaluated at NIH, have a history of bites from juvenile Ambylomma americanum, or Lone Star ticks.

Among the study participants with alpha-gal allergy evaluated at NIH, two also had a rare condition called indolent systemic mastocytosis, or ISM. People with ISM have an abnormally elevated number of mast cells, an immune cell type which contributes to anaphylaxis and other allergic symptoms by releasing histamine and other chemicals that cause inflammation. The participants with ISM experienced more severe reactions than those without ISM, even though they had lower levels of antibodies to alpha-gal. This finding builds on evidence that mast cell abnormalities may increase the likelihood of people developing allergies and experiencing severe reactions, including allergies and reactions to alpha-gal.

Alpha-gal syndrome (AGS) (also called alpha-gal allergy, red meat allergy, or tick bite meat allergy) is a serious, potentially life-threatening allergic reaction. AGS is not caused by an infection. AGS symptoms occur after people eat red meat or are exposed to other products containing alpha-gal.

• Alpha-gal (galactose-α-1,3-galactose) is a sugar molecule found in most mammals.
• Alpha-gal is not found in fish, reptiles, birds, or people.
• Alpha-gal can be found in meat (pork, beef, rabbit, lamb, venison, etc.) and products made from mammals (including gelatin, cow’s milk, and milk products).

Food allergies affect 5 percent of children and 4 percent of adults in the U.S. The number of people with food allergies is rising without a known cause.

What is a food allergy?

In a person with a food allergy, the immune system reacts abnormally to a part of a food. Sometimes the response can be life-threatening.

What foods commonly cause an allergy?

Foods that often cause allergic reactions in adults include fish, shellfish, peanuts, and tree nuts, such as walnuts. Problem foods for children can include eggs, milk, peanuts, tree nuts, soy, and wheat.

What are symptoms?

The allergic reaction may be mild. In some cases, foods can cause a severe reaction called anaphylaxis.

Symptoms of a food allergy include:

• Itching or swelling in your mouth
• Vomiting, diarrhea, or abdominal cramps and pain
• Hives or eczema
• Tightening of the throat and trouble breathing
• Drop in blood pressure

What types of treatment are there?

Health care providers can help manage patients' food allergies by encouraging them to avoid foods that may cause an allergic reaction and by treating severe reactions when they happen. Additionally, the National Institute of Allergy and Infectious Diseases (NIAID) is researching new ways to help treat and manage food allergies.

Anyone could get AGS.

• Most reported cases of AGS in the United States are among people living in the South, East, and Central United States.
• While people in all age groups can develop AGS, most cases have been reported in adults.

• Growing evidence suggests that AGS may be triggered by the bite of a lone star or blacklegged tick in the United States. Other tick species have been connected with the development of AGS in other countries.
• More research is needed to understand the role ticks play in starting this reaction, and why certain people develop AGS.

Researchers found that some people’s repeated, severe allergic reactions stemmed from a red meat allergy linked to a specific type of tick bite.

Doctors analyzed 70 patients who had repeated episodes of a severe allergic reaction, called anaphylaxis, from unknown causes. Anaphylaxis can cause a host of problems, such as trouble breathing and passing out. It requires immediate medical attention to prevent severe consequences, even death.

The researchers found that six of the patients had an allergy to a sugar molecule called alpha-gal, which is found in red meats. Most food allergy symptoms develop within a half hour. People with the alpha-gal allergy showed symptoms between three to six hours after eating meat.

Previous studies have linked lone star tick bites to this unusual food allergy. The patients with the alpha-gal allergy lived in the central and southern United States, where lone star ticks thrive. All six confirmed that they had been bitten by ticks in the past.

“Alpha-gal allergy appears to be yet another reason to protect oneself from tick bites,” says Dr. Anthony S. Fauci, director of NIH’s National Institute of Allergy and Infectious Diseases (NIAID).

• AGS reactions can include:

  • Rash
  • Hives
  • 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
• Symptoms commonly appear 2-6 hours after eating meat or dairy products, or after exposure to products containing alpha-gal (for example, gelatin-coated medications).
• AGS reactions can be different from person-to-person. They can range from mild to severe or even life-threatening. Anaphylaxis (a potentially life-threatening reaction involving multiple organ systems) may need urgent medical care.
• People may not have an allergic reaction after every alpha-gal exposure.
• If you think you may have AGS go talk to your healthcare provider.

AGS can be severe, and even life-threatening. Seek immediate emergency care if you are having a severe allergic reaction.

• AGS is diagnosed by an allergist or other healthcare provider through a detailed patient history, physical examination, and a blood test that looks for specific antibodies (proteins made by your immune system) to alpha-gal.
• Your healthcare provider may also recommend allergy skin testing.

• AGS should be treated and managed under the care of an allergist or other healthcare provider.
• Many foods and products contain alpha-gal; you will need to work with your healthcare provider to understand which products you need to avoid.
• Prevent tick bites. New tick bites may reactivate allergic reactions to alpha-gal.

AGS can be severe, and even life-threatening. Seek immediate emergency care if you are having a severe allergic reaction.

Not all patients with AGS have reactions to every ingredient containing alpha-gal. The following foods or food ingredients may contain alpha-gal. This is not a list of all products or ingredients that may contain alpha-gal.

• Mammalian meat (such as beef, pork, lamb, venison, rabbit, etc.) can contain high amounts of alpha-gal.

  • Certain cuts of meat may contain more alpha-gal than others. For example, organ meat of mammals, including liver, lung, heart, kidneys, intestines (tripe), sweetbreads, scrapple, and Rocky Mountain or prairie oysters generally contain high amounts of alpha-gal.
• Food products that contain milk and milk products typically contain alpha-gal.
  • Many patients with AGS can tolerate milk products.
  • Cow’s milk is the only alpha-gal containing ingredient classified as a major food allergen. Under the Food Allergen Labeling Requirements of the Food, Drug, and Cosmetic Act, food labels must clearly identify the food source names of any ingredients that are one of the major food allergens or contain protein derived from a major food allergen in the ingredient list or a separate “Contains” statement.
• Some people with AGS may also be sensitive to alpha-gal found in
  • Gelatin made from beef or pork
  • Products made from or cooked with mammalian fat (such as lard, tallow, or suet)
  • Meat broth, bouillon, stock, and gravy

Foods that do NOT contain alpha-gal:

• Poultry, such as chicken, turkey, duck, or quail
• Eggs
• Fish and seafood, such as shrimp
• Fruits and vegetables

• Some medications and vaccines may contain small amounts of alpha-gal-containing additives, stabilizers, or coatings. Not all patients with AGS react to these ingredients.
• Ingredients that may contain alpha-gal include, but are not limited to:
  • Gelatin
  • Glycerin
  • Magnesium stearate
  • Bovine extract
• Other medical products, such as heart valves from pigs or cows, monoclonal antibodies, heparin, and certain antivenoms are animal-derived and may contain alpha-gal.
• As with any severe allergy, patients with AGS should work with their healthcare providers to make decisions about individual risk and benefit from specific vaccines and medications.

Preventing tick bites is important in preventing tickborne disease and may reduce your chances of developing AGS.

• Before you go outdoors

• • Avoid grassy, brushy, and wooded areas, where ticks may be found.
  • Treat clothing and gear with permethrin or buy pre-treated items.
  • Use Environmental Protection Agency (EPA)-registered insect repellents.
• After you come indoors
  • Check your clothing for ticks.
  • Shower and perform a thorough tick check.
• If you see an attached tick, remove it immediately.
• Take steps to prevent ticks on your pets and in your yard.