Are ticks causing a “red meat” allergy? Scientists are trying to understand unexplained anaphylaxis incidents

Most allergies hit a person immediately after exposure: Symptoms are bound to develop immediately, from itchy hives to swelling, and even anaphylactic shock. The reactions can be dangerous and potentially fatal, but most of these can be identified and treated immediately.

However, some people experience allergic reactions that seem to come out of nowhere. Recurring episodes of anaphylaxis (a serious allergic reaction which causes constriction of airways and a dangerous drop in blood pressure) for which the triggers are never identified have left both sufferers and doctors puzzled until recently.

A study published by researchers at the National Institutes of Health have found that some patients’ inexplicable allergic reactions were triggered by a molecule found in red meat. They continue by saying that this type of allergy, which can be difficult to identify, has an unlikely culprit — a tick.

Allergic reactions caused by a bite from the Lone Star tick can be delayed. Unlike other types of allergies, reactions can occur from three to 12 hours after eating red meat. This puts sufferers at a disadvantage, as identifying the trigger at the onset may prove to be difficult. The study also adds that this delayed reaction has caused physicians to mistakenly diagnose patients with this allergy as having unexplained anaphylaxis.

“This unusually long time gap between a meal and an allergic reaction is probably a big reason that alpha-gal allergies are often initially misdiagnosed,” says Dr. Dean Metcalfe, chief of the Mast Cell Biology Section in the Laboratory of Allergic Diseases at the National Institute of Allergy and Infectious Diseases. “If you start to have trouble breathing in the middle of the night, you probably are not going to blame the hamburger you had for dinner.”

The reasons for the delay are unknown, with some episodes starting during sleep, and they usually hit hard: aside from an anaphylactic reaction, common symptoms also include shortness of breath and a breakout of hives.

Dr. Ronald Saff of the Florida State University College of Medicine puts it bluntly: “They’re sleeping, and they have no idea what they could be allergic to because the symptoms occurred so many hours after going to bed.”

In the study, six of the 70 study participants that were evaluated were positive for an allergy to galactose-?-1,3-galactose, or alpha-gal, a sugar molecule that is naturally present in red meat. After the allergen was identified, participants were subjected to a diet without red meat in a span covering 18 months to three years. It was noted that none of them experienced anaphylaxis during those times. (Related: Eating Meat Kills More People Than Previously Thought.)

Still, there are many things that we do not know about the allergic reaction to alpha-gal (also known as the “alpha-gal syndrome”) — one of which is its prevalence across the country. So far, the Lone Star tick is common in the Southeast; however, cases of the alpha-gal syndrome have already been noted in areas like Minnesota, New Hampshire, and even Long Island.

While experts know that a bite from the Lone Star tick causes changes in a person’s sensitivity to a sugar compound, it is still unclear how this change affects a person — with the degree of sensitivity varying from person to person. There have been reports of people becoming severely allergic that they are unable to consume animal products like dairy milk.

Additionally, the duration that a person stays allergic to red meat after being exposed to the bite is also uncertain.

Sources include

NIAID.NIH.gov

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