North Carolina is seeing an increase of patients developing an allergy to galactose-alpha-1,3-galactose (also known as alpha-gal), a sugar found in lower mammals such as cows and pigs but not great apes or humans. As a result, patients become allergic to red meat.
A lot of mystery surrounds the allergy, but doctors suspect that it’s caused by tick and chigger bites.
“One hypothesis is that tick bites are causing the allergic reaction by introducing the alpha-gal carbohydrate into the human body,” says Scott Commins, MD, PhD, an allergist and researcher at the UNC Thurston Arthritis Research Center who specializes in the alpha-gal allergy. The center is one of a few places in the U.S. conducting alpha-gal research.
Alpha-Gal Allergy Symptoms
The mammalian meat allergy—this doesn’t include poultry—can be difficult to diagnose because it doesn’t present like typical food allergies. The symptoms are indicative of many other health issues. However, there is a degree of variation in the number and severity of symptoms a patient suffers.
Possible reactions include:
- Abdominal cramping and pain
- Itchy hands and feet
- Flushed skin
- Trouble swallowing
Why The Alpha-Gal Allergy Is Tough to Diagnose
The alpha-gal meat allergy is difficult to diagnose for several reasons, leading to prolonged and sometimes increased suffering for patients. Factors that can make it difficult to diagnose include:
- The allergic response comes hours after ingesting the sugar.
- There can be variation in symptoms (for example, some people have diarrhea, some have hives).
- Allergic reactions can be inconsistent, not occurring after every ingestion.
- Symptoms can sometimes be mild.
Alpha-Gal IgE Testing
The alpha-gal IgE blood test—testing for immunoglobulin E antibodies made by the immune system—is the best way to make the diagnosis. Providers should run the blood test for alpha-gal IgE in patients who present with hives, itching or GI symptoms that occur sporadically and without obvious cause, especially when these episodes occur at night.
Testing, via a blood draw, can be done at the UNC Allergy and Immunology Clinic.
The Alpha-Gal Diet
After positive diagnosis from a blood test, patients should avoid all forms of mammalian meat as the first step. (Besides cow and pig, that means lamb, venison, bison, goat and rabbit, for example.) If symptoms persist, patients should remove mammalian animal products such as milk and cheese from their diets.
To avoid cross-contamination, it’s also important to make sure there are no animal products in foods that aren’t typically associated with red meat. For example, sometimes green beans or other vegetables are cooked with pork products, and vegetable soup is often made with beef broth. Patients should avoid anything containing the alpha-gal sugar.
Prevalence of the Mammalian Meat Allergy
Calculating the prevalence of the alpha-gal allergy is difficult because geography appears to play a large role in the number of people who experience the allergic reaction.
For example, while it appears there are more than 3,000 cases in the Southern and Eastern United States, there are few cases in Denver because ticks don’t tend to live in high-altitude climates.
In North Carolina, more than 1,000 patients have been diagnosed with the alpha-gal allergy, with a comparatively high concentration of cases in Chatham County (specifically Pittsboro) and Johnston County.
Alpha-Gal Anaphylaxis: One Patient’s Battle
One Chapel Hill resident we will call Jane has suffered anaphylaxis from ingesting alpha-gal numerous times over the past six years. She’s an avid gardener who lives in a woodsy area and for whom tick bites are a part of life.
“I think ticks are more attracted to me than other people,” Jane says.
After her first anaphylactic episode, Jane began keeping a food journal, but she still remained mystified by her severe allergy.
That’s when she was referred to Maya Jerath, MD, PhD, an allergist with the UNC Allergy and Immunology Clinic.
“Maya helped me understand the allergy and helped me deal with the adjustment to a new kind of life,” Jane says. “Treatment went beyond diet restrictions. It was also about coping with this emotionally challenging condition and finding a support system.”
It’s difficult for Jane to keep the allergy at bay, cooking for four omnivorous boys. Last summer she had three anaphylactic episodes in one month, despite avoiding mammalian meat. She can only suspect cross-contamination as the cause.
For some patients, the allergic response improves over a few years, but in Jane’s case, it seems to only be getting worse six years later. She gets alpha-gal IgE tests regularly at her primary physician’s office. Ongoing testing can be helpful because the allergy often will resolve over time, when there haven’t been additional tick bites.
Contact the UNC Allergy and Immunology Clinic to learn more about the alpha-gal IgE test. You can call (984) 974-2645.
About Dr. Commins
Scott Commins, MD, PhD, is an allergist at the UNC Allergy and Immunology Clinic and an associate professor at the UNC School of Medicine.