November 9, 2015

Tick bite can cause red meat allergy


After a lone star tick bite, reactions can range from itching to anaphylactic shock.

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

Vanderbilt’s Asthma, Sinus and Allergy Program (A.S.A.P.) clinic has seen many people in recent years who are allergic to alpha-gal, a type of sugar present in red meat.

The lone star tick has alpha-gal sugar in its gut, and introduces it to a person’s system when it bites. The human immune system produces an antibody that reacts if the person eats meat.

The allergy can cause hives, swelling and broader symptoms of anaphylaxis (hypersensitivity), including vomiting, diarrhea, trouble breathing and a drop in blood pressure.

People who develop an allergy to the alpha-gal sugar can safely eat poultry such as chicken or turkey, but red meats such as beef and pork, and even game, including venison, will cause a reaction. Some patients react to milk.

Delayed reactions

The allergic reaction can happen four to six hours after eating red meat, and the delay makes diagnosis tricky. When Hendersonville resident September Norman woke up one night in July 2013 with a swollen tongue and hives, for example, she didn’t know what triggered the problem.

Norman and her husband were staying at Tennessee’s Fall Creek Falls State Park at the time. They had played golf, then grilled ribeye steaks for dinner.

“At about midnight I woke up and was itching very bad, kind of like a rash,” she said. “About 2:30 a.m. I got up and my hands felt like they were on fire, like I was 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 that something was wrong. I could barely talk at that point, my tongue was so thick. He turned on the lights and his eyes looked like saucers.”

They drove from the park toward the interstate to get a cell phone signal to call 911 and waited on the highway for emergency help to arrive.

“I was getting worse. My whole body was red and broken out in hives. I was staring out the window, saying ‘Please God, not here.’ I probably would have gone into a panic had I looked at myself in the mirror. My husband said my face looked like a giant red balloon and my lips looked like a clown.”

Carry an EpiPen

The emergency responders gave Norman an epinephrine injection to treat the anaphylaxis, and she received Benadryl, an IV and steroids during the ambulance ride to Sparta, the closest hospital. The doctor at the hospital 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, even preparing her son’s favorite pork tenderloin dish that Wednesday. As the week wore on, and her steroids from the hospital wore off, Norman felt her throat becoming tighter and tighter.

“I had been eating the culprits all week,” she said. “I was full of steroids and that’s probably why it took so long. We went to Vanderbilt and Dr. Jan Price, a primary care doctor, talked to me about what happened to me. I was retracing my steps and remembered that, in the middle of June, a tick bit me on the foot.” Dr. Price sent Norman to the A.S.A.P. clinic, where she was diagnosed with the allergy.

The diagnosis is done with a blood test. But there is not a good way to desensitize people once they develop this allergy, so they have to avoid red meat and, in some cases, milk as well.

Getting repeated tick bites causes the level of allergy antibody to rise. Allergists recommend that people with this allergy take careful steps to avoid ticks, and carry an EpiPen in case they unintentionally consume red meat.

Craig Boerner is media director, national news director and a senior information officer for Vanderbilt University Medical Center. This article first appeared in the Vanderbilt Reporter on Feb. 20, 2014.