NIAID Scientists Link Unexplained Anaphylaxis to Red Meat Allergy
While rare, some people experience recurrent episodes of anaphylaxis—a life-threatening allergic reaction that causes symptoms such as the constriction of airways and a dangerous drop in blood pressure—for which the triggers are never identified. Recently, researchers at NIAID found that some patients’ seemingly inexplicable anaphylaxis was actually caused by an uncommon allergy to a molecule found naturally in red meat. They note that the allergy, which is linked to a history of a specific type of tick bite, may be difficult for patients and health care teams to identify.
As the researchers describe in their article published in Allergy, 6 of the 70 study participants evaluated for unexplained frequent anaphylaxis tested positive for an allergy to galactose-a-1,3-galactose, or alpha-gal, a sugar molecule found in beef, pork, lamb and other red meats. The six adult male participants all had IgE antibodies—immune proteins associated with allergy—to alpha-gal in their blood. After implementing diets free of red meat, none of them experienced anaphylaxis in the 18 months to 3 years during which they were followed.
While the prevalence of allergy to alpha-gal, or “alpha-gal syndrome” is not known, researchers have observed that it occurs mostly in people living in the Southeast region of the United States and certain areas of New York, New Jersey and New England. This distribution may occur because most people with an allergy to alpha-gal, including all six participants evaluated at NIH, have a history of bites from juvenile Ambylomma americanum, or Lone Star ticks.
“Alpha-gal allergy appears to be yet another reason to protect oneself from tick bites,” said NIAID director Dr. Anthony Fauci. “Food allergies can range from an inconvenience to a life-threatening condition and pose a serious and growing public health problem that urgently requires more research.”