The culprit is the Lone Star tick. The bugs harbor a sugar that humans don't have, called alpha-gal. The sugar is also is found in red meat — beef, pork, venison, rabbit — and even some dairy products. It's usually fine when people encounter it through food that gets digested. But a tick bite triggers an immune system response, and in that high-alert state, the body perceives the sugar the tick transmitted to the victim's bloodstream and skin as a foreign substance, and makes antibodies to it. That sets the stage for an allergic reaction the next time the person eats red meat. At the University of Virginia in Charlottesville, "I see two to three new cases every week," said Dr. Scott Commins, who with a colleague, Dr. Thomas Platts-Mills, published the first paper tying the tick to the illness in 2011.
See more from NBC News.
Copyright 2015 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.