Ticks and red meat allergy

From the Summer 2014 edition of Vanderbilt Medicine Magazine

Lone star tick bites are likely the cause of thousands of cases of severe red meat allergies that are plaguing patients in Southeastern states including Tennessee, North Carolina and Virginia and spreading up the Eastern Seaboard along with the deer population.

Vanderbilt’s Asthma, Sinus and Allergy Program (A.S.A.P.) clinic is seeing one or more new cases each week of patients allergic to the alpha-gal sugar present in red meat, according to Robert Valet, M.D., assistant professor of Medicine.

“It is not completely understood exactly how the allergy starts,” Valet said. “The thought is that the tick has the alpha-gal sugar in its gut and introduces it as part of the allergic bite and that causes the production of the allergy antibody that then cross-reacts to the meat,” he said.

Valet said the allergy can cause hives and swelling, as well as broader symptoms of anaphylaxis including vomiting, diarrhea, trouble breathing, and a drop in blood pressure.

“I think it is something that certainly belongs among the most important food allergies, particularly in the Southeast,” he said. “Certainly these patients can present with every bit as severe of an allergy as someone who is allergic to peanuts.”

Alpha-gal patients can safely eat poultry such as chicken or turkey but red meats such as beef and pork, and even game like venison, will cause a reaction. Valet said some patients react to milk, even in relatively small amounts.

Persons with the allergy can go into a delayed anaphylactic shock four-six hours after eating red meat. Valet said he diagnoses patients with a blood test but there is not a good way to desensitize people once they become allergic to this food, so they have to avoid red meats and, in some cases, milk as well.

“It certainly is a big disruption for a lot of people’s lives. Things like your classic barbecue really becomes off limits,” Valet said. “We know that getting repeated tick bites causes the level of allergy antibody to rise and so we do recommend people with this allergy do good tick avoidance and carry an EpiPen if they do have an exposure to red meat and need to rescue themselves.”

– Craig Boerner