As Americans head outdoors for barbeques or hiking in the woods, danger might be lurking in the grass. The bite of the lone star tick, which lives in many eastern U.S. states, has been known to cause an allergic reaction to red meat. New research suggests that meat allergy may be on the rise.
Mammalian meat allergy, also known as the alpha-gal allergy, refers to an allergic reaction caused by a complex sugar found in many mammalian cell membranes. The galactose-alpha-1,3-galactose sugar isn’t found in primates (including humans), but is common to red meats such as pork and beef.
Symptoms of meat allergy can include hives, stomach trouble, and a sudden drop in blood pressure. It can lead to anaphylaxis, a severe and potentially life-threatening allergic reaction. New research by Dr. Jay Lieberman at the University of Tennessee Health Science Center finds one-third of anaphylaxis cases in a recent 10-year period were caused by this arachnid-induced allergy.
Lieberman and his co-authors were interested in assessing the breakdown of various causes of anaphylaxis, including the alpha-gal (red meat) allergy.
Anaphylaxis is usually defined as a reaction involving at least two different organ systems.
“For example, if you have full body hives and you vomit,” Lieberman said, “that can be anaphylaxis, as long as you know that it’s not associated with an infection or virus.”
The researchers evaluated 218 cases of anaphylaxis in patients ranging from as young as 9 years old to 78-year-old retirees who visited their university-affiliated Tennessee clinic over a 10-year period.
By reviewing the patients’ medical records, the doctors could identify the cause of the allergic reactions with high certainty in 85 of the cases and relative certainty in an additional 57 cases.
Researchers found that of the 85 highly certain cases, 28 -- or about one-third -- were caused by the tick-bite-induced alpha-gal allergy, more than any other source including other food allergies like peanuts or shellfish.
In the 57 cases where the researchers were less certain of the cause of the allergic reaction, they found more than a quarter of the cases were most likely caused by alpha-gal. Taken together, the meat allergy was the most commonly identified source of anaphylaxis in those 142 cases.
Lieberman told VOA not every tick bite leads to an immune system reaction and not everyone with antibodies caused by the tick bite ends up with this meat allergy. “Clearly there are many people who get bitten by ticks that probably never develop the allergy to alpha-gal."
However, experts say that knowledge of the tick-borne allergy since its formal recognition in the early 2000s, as well as an antibody blood test that helps identify it, has helped spread awareness about it. This comes as the range of the lone star tick is also spreading, north and west from the eastern United States and Mexico.
Lieberman noted that while the number anaphylaxis cases caused by alpha-gal has increased, the number of unidentified cases has also decreased.
“These patients were there before and we didn't know what it was,” he said. Lieberman further explained that with the advent of a testing method for alpha-gal allergy, these patients are now getting the diagnosis they would have missed before.
Dr. Onyinye Iweala, at the University of North Carolina Division of Rheumatology, Allergy and Immunology, who was not involved in the study, said the findings might be due to two reasons.
“I think [the alpha-gal allergy] has been present for a while, but it’s increasing in its prevalence,” Iweala told VOA. “And also we have better diagnostics to identify that people have this condition.”
However, Lieberman warns it can be hard for an afflicted person to recognize the symptoms because they have up to several hours delayed onset.
Speaking on the uniqueness of the alpha-gal allergy, he said, “It’s the only one we know of that’s a delayed allergy, so it can even present in the middle of the night. You eat dinner at 8 p.m., you go to bed at 11 and you wake up at 1 a.m. with these symptoms.”
Although Lieberman’s research was conducted in the heart of lone-star tick country in Tennessee, Iweala notes that the meat allergy isn’t a uniquely American problem.
“Meat allergy has been discovered in multiple countries in Europe, Australia, Japan and also in South Africa,” she said. “They're different tick species that have been identified in Europe and in Australia that have been associated with the alpha-gal allergy,” but the resulting allergy to red meat remains the same.
While people affected can still eat fish and poultry, the allergy might make neighborhood barbecues with hotdogs and hamburgers less enjoyable. Researchers note that the allergy can lessen or even disappear in some people over time. Still many questions remain, including why the allergy seems to be on the rise.
This research was published Monday by the American College of Allergy, Asthma, and Immunology, where Dr. Lieberman is the vice chair of the food allergy committee.