Meat Allergies Likely Result of Tick Bites
Lone star tick bites are likely the cause of thousands of cases of severe red-meat allergies plaguing patients in Southeastern states and spreading up the Eastern Seaboard.
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 Dr. Robert Valet, MD’05, assistant professor of medicine. Alpha-gal (short for galactose-alpha-1, 3-galactose) is a sugar carbohydrate found in the red meat of nonprimate mammals.
“It is not completely understood exactly how the allergy starts,” Valet says. “The thought is that the tick has the alpha-gal sugar in its gut and introduces it as part of the allergic bite, which causes the production of the allergy antibody that then cross-reacts to the meat.”
The allergy can cause hives, swelling, and broader symptoms of anaphylaxis including vomiting, diarrhea, trouble breathing, and a drop in blood pressure. “Certainly, these patients can present with every bit as severe of an allergy as someone who is allergic to peanuts,” says Valet.
Alpha-gal patients can safely eat poultry, but red meats such as beef and pork, and game like venison, will cause a reaction. Some patients react to milk. The allergy can produce a delayed anaphylactic shock four to six hours after eating red meat.
That’s what happened to Hendersonville, Tenn., resident September Norman last July. While staying at Tennessee’s Fall Creek Falls State Park, she and her husband played some golf and then grilled rib-eye steaks for dinner.
“At about midnight I woke up and was itching very badly, kind of like a rash,” she remembers. “About 2:30 a.m. I got up and my hands felt like they were on fire, like I’d been bitten by fire ants. I drank two bottles of water, sat on the sofa, and it wasn’t five minutes before I felt my tongue and lip swelling and told my husband something was wrong. I could barely talk at that point, my tongue was so thick.”
They drove from the park toward the interstate to get a cellphone signal to call 911.
“I was getting worse,” says Norman. “My whole body was red and broken out in hives. I was staring out the window, saying, ‘Please, God, not here.’”
Emergency responders gave Norman an epinephrine injection, and she received Benadryl, an IV and steroids during the ambulance ride to Sparta, the closest hospital. The doctor there said her reaction was probably environmental and sent her home with a prescription and advice to always carry an EpiPen.
She continued to eat red meat, and as the week wore on and her steroids from the hospital wore off, Norman felt her throat becoming tighter and tighter.
“We went to Vanderbilt, and Dr. Jan Price talked to me about what happened to me,” she recalls. “I was retracing my steps and remembered that, in the middle of June, a tick had bitten me on the foot. She sent me to Dr. Valet, and he said he knew what I had based on the tick and my reactions.”
“Things like your classic barbecue really become off-limits,” says Valet. “We know that repeated tick bites cause the level of allergy antibody to rise, and so we recommend people with this allergy to practice good tick avoidance and to carry an EpiPen in case they have an exposure to red meat and need to rescue themselves.”