Tick-Borne Red Meat Allergy Was Most Common Cause of Reactions, Study Shows

When we talk about allergies, we usually think of pollen, peanuts, or pets. But there’s a new kid in town, and doctors say it’s even more common than they previously thought. Spread by the lone star tick, an allergy to red meat (pork, beef, and other mammals) is on the rise. This allergy presents as anaphylaxis, just like other potentially life-threatening allergies, causing swelling and itchiness. It’s triggered by galactose-alpha-1,3-galactose — alpha-gal for short — a carbohydrate in the flesh of some mammals. And in a study of patients at a clinic in Tennessee, a team of doctors found that alpha-gal was actually the most common source of anaphylactic reactions.

In a paper published Monday in the journal Annals of Allergy, Asthma & Immunology, doctors at an allergy and immunology clinic at the University of Tennessee show evidence that allergies to alpha-gal were the most common cause of anaphylaxis among patients over a period of 10 years. Out of 218 anaphylaxis cases in a retrospective analysis of medical records, the doctors identified 85 as having a definite cause, as opposed to having a probable or unknown cause. And out of these 85 patients, the doctors concluded that 28 of them, nearly one-third, could be attributed to alpha-gal allergy.

Notably, this study’s results are very different from the same clinic’s previous studies of the top causes of allergies. In the past, the doctors had identified a much higher proportion of anaphylaxis cases that were idiopathic, which means they arise spontaneously and have no known cause. But with better testing, they were able to move a bunch of cases from the “idiopathic” column into the “alpha-gal” column.

“When compared to the previous reports from our center, the number of idiopathic anaphylaxis cases decreased from 59% of cases reviewed from 1978-2003 to the currently reported 35% of cases,” write the study’s authors.

The reason for this improvement? In the years since the clinic’s last assessment in 2006, doctors have figured out what’s causing the alpha-gal allergy: an immunoglobin E (IgE) antibody that triggers anaphylaxis when a person consumes mammal flesh. Scientists have only discovered this mechanism in the past 10 years, but since the identification of the IgE antibody responsible for alpha-gal allergy, doctors have been able to test patients and figure out exactly why they’re waking up itchy and sweating in the middle of the night after eating ribs. And not only did they figure out what’s wrong with these mystery patients, they actually discovered that these patients were afflicted with an allergy that’s the most common reaction, at least in Tennessee.

“With increased awareness and widely available diagnostic testing for specific IgE to alpha-gal, alpha-gal allergy evolved from an unknown entity to the most commonly identified cause of anaphylaxis in our current analysis,” write the study’s authors.

This study comes at a good time, as the US Centers for Disease Control and Prevention says the lone star tick’s range is expanding, and there’s still no known cure for the allergy. So even though more people may become allergic to red meat, improvements to testing and diagnosis mean that a lot of people will at least start to get answers about their unexplained allergies.