The most common cause of anaphylaxis cases in a Tennessee allergy clinic stemmed from an allergic reaction to alpha-gal - a sugar found in red meat such as beef, pork and venison - caused by ticks, according to a recent study.
The clinic also saw unknown anaphylaxis cases decrease from 59 percent to 35 percent. Researchers attributed the trend to an increase in lone star tick populations and a heightened awareness of alpha-gal allergy, which was first discovered in 2008.
Dr. Michael Hollie, a physician at the Allergy and Asthma Group of Galen, said the study adds to a growing body of literature and demonstrates that alpha-gal allergy is a significant source of anaphylaxis - a potentially life-threatening allergic reaction characterized by skin rash, nausea, vomiting, trouble breathing and shock.
"Over the last several years, it's more clear that tick bites seem to be, in most cases, a preceding event, specifically that lone star tick that's really common in the Southeast," Hollie said. "When they bite humans, they inject a little bit of [alpha-gal] into the bloodstream, and for reasons that we don't fully understand, some people's immune system reacts to that sugar and creates an allergic antibody."
The latest study found that that 33 percent of the 218 anaphylaxis cases reviewed were caused by alpha-gal, said Dr. Debendra Pattanaik, an associate professor of rheumatology in the University of Tennessee College of Medicine and principal investigator of the study.
"Our research clearly identified alpha-gal as the cause of anaphylaxis in the majority of cases where the cause was detected. Food allergies were the second leading cause, accounting for 24 percent," Pattanaik said in a news release. "When we did the same review in 1993, and again in 2006, we had a great many cases where the cause of the anaphylaxis couldn't be identified."
Hollie said sometimes it's difficult to determine the cause of anaphylaxis, and initially pinpointing the alpha-gal allergy was especially tricky, because the allergic reaction is often delayed, whereas most cases of anaphylaxis caused by food are immediate.
"A very common scenario is that someone will eat dinner in the evening, and that dinner will contain some sort of beef, lamb, or pork, then they'll wake up in the middle of the night with maybe some nausea, vomiting, hives, skin rash," he said.
While anaphylaxis is a serious medical condition, it's preventable by avoiding known allergens and carrying an epinephrine injection to counteract any reactions. Hollie also said some patients eventually overcome their allergy to alpha-gal.
Contact staff writer Elizabeth Fite at efite@timesfreepress.com or 423-757-6673.