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Odd Red Meat Allergy May Be Behind Some Mysterious Allergic Reactions
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Some people who experience seemingly mysterious allergic reactions may have a rare type of allergy to red meat, a new study finds.

The study evaluated 70 people who had "unexplained frequent anaphylaxis," which means they had life-threatening allergic reactions that didn't have an apparent trigger.

About 9 percent of these participants tested positive for an allergy to a molecule called galactose-alpha-1,3-galactose, or "alpha-gal," which is found in beef, pork, lamb and other red meats. When these patients cut red meat out of their diet, none of them experienced anaphylaxis during the 1.5-to-three-year follow-up period, the researchers said.

Diagnosing an alpha-gal allergy can be a challenge, in part because patients with the condition often experience a delayed allergic reaction that occurs about 3 to 6 hours after they consume red meat, the researchers said. In contrast, most allergic reactions to other foods occur about 5 to 30 minutes after a person consumes the food. [9 Weirdest Allergies]

"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," Dr. Dean Metcalfe, chief of the Mast Cell Biology Section at the National Institute of Allergy and Infectious Diseases (NIAID) and co-author of the study, said in a statement. (Mast cells are a type of immune cell that plays a role in allergies.) "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," Metcalfe said.

What's more, most routine allergy tests do not check for alpha-gal allergies. The researchers said their new study "supports the need for routine screening for this sensitivity as a cause of anaphylaxis," they concluded.

Interestingly, people with alpha-gal allergies often have a history of tick bites from lone star ticks(Amblyomma americanum). Indeed, in the current study, all of the patients with alpha-gal allergies had experienced lone-star-tick bites. Earlier research suggested that these tick bites can play a role in causing this rare allergy.

"We often think of ticks as carriers of infectious diseases, such as Lyme disease, but the research strongly suggests that bites from this particular species of tick can lead to this unusual allergy," said study co-author Dr. Melody Carter, also of the Mast Cell Biology Section at NIAID. "The association is increasingly clear, but we still need to discover exactly how these two events are linked and why some people with similar exposure to tick bites seem to be more prone to developing alpha-gal allergy than others."

The new study was published online Nov. 21 in the journal Allergy.

Original article on Live Science.