A few years ago an outbreak of red meat allergy cases in the southeastern U.S. had health officials scratching their heads. Eventually, it was suspected that the spike in red meat allergies was linked to the bite of the lone star tick. And now, scientists claim to have unraveled the mystery of exactly why a tick bite could banish you from the world of beef.
Meat allergy mystery
Food allergies are immune system reactions. As antibodies attack the food, such as peanuts, that causes the reaction they release histamines, chemicals that trigger hives and, in severe cases, anaphylaxis. Anaphylactic shock is a life-threatening system-wide dilation of blood vessels that causes a rapid drop in blood pressure.
The mystery of the tick bite meat allergy began back in 2008 when scientists at the University of Virginia in Charlottesville wanted to know why a cancer drug called Erbitux was causing severe allergic reactions to patients in southern states. Their findings suggested that affected patients carried an antibody, Immunoglobulin E (IgE), that reacted to sugars in Erbitux known as alpha-gal that are also found in beef, pork and cow’s milk.
Connecting the dots
About a year later a dramatic increase in the number of healthy people in the south coming down with red meat allergies made headlines. The UVA researchers connected the dots. They began testing blood samples from newly-meat allergic people and found that they carried the same antibodies as the cancer patients allergic to the alpha-gal sugars in Erbitux.
The researchers believed a parasite could be the culprit. It wasn’t clear which parasite until the lead researcher, Thomas Platts-Mills, measured elevated IgE and alpha-gal levels in his own blood a few days after he suffered numerous tick bites on a hike in the woods.
The researchers then began asking about 1,500 patients who had reported a reaction if they had been bitten by ticks before their meat allergy developed. More than 90 percent said they did.
An uncommon allergy
New research published in online in the July issue of the Journal of General Internal Medicine sheds more light on exactly how a tick bite can lead to a red meat allergy. After examining three test cases, it became evident that the saliva of a specific tick endemic to the south–the lone star tick–contains alpha-gal sugars.
The body develops the IgE antibody in response to the alpha-gal—the same carbohydrate in red meat. The next time the tick victim eats meat again, their immune system attacks the body, causing an allergic reaction that hits about three to six hours after eating meat.
The red meat allergy is unique because it’s the only allergy where anaphylaxis is delayed, instead of happening instantly upon exposure like with peanuts, for example. It’s also the first known food allergic reaction triggered by a carbohydrate instead of a protein.
Once bitten, barbecue shy
Dr. Scott Commins, an assistant professor of medicine at UVA working on the project, told Food Safety News unfortunately there’s not much you can do to avoid developing a red meat allergy once you’ve been bitten. “My sense is the bite itself is enough to cause the allergy to happen,” he said. “They don’t have to be attached for very long at all.”
The good news is that the allergy appears to fade in 3-5 years. However, if you’re bitten again, the allergy could be more severe and last even longer.
Developing any kind of allergy is nothing to sneeze at. But eating a lot of red meat is associated with cardiovascular disease, cancer and other chronic illnesses. Would you feel better off big juicy steaks became an even bigger hazard to your health?