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• Posted March 27, 2023

Tick Bites Can Trigger Meat Allergy: What You Need to Know

If you are experiencing mysterious recurrent vomiting, diarrhea and abdominal pain, you may want to consider that a tick could be responsible.

When the lone star tick bites a person, it can transmit something called "alpha gal,"the sugar that's present in all mammals except humans, explained Dr. Sarah McGill. She is an associate professor of gastroenterology and hepatology at the University of North Carolina School of Medicine in Chapel Hill.

That transmission can lead to alpha-gal syndrome, a tick-borne meat allergy. If you have it, you might have gastrointestinal (GI) symptoms several hours after eating meat and sometimes milk products.

McGill is lead author of a clinical practice update on the GI effects of alpha-gal syndrome published in the April issue of the journal Clinical Gastroenterology and Hepatology.

"We want the update to raise awareness,"McGill said in a university news release. "When a patient has symptoms such as abdominal pain, diarrhea, nausea, vomiting -- which admittedly are very nonspecific -- among the things we want people to think about is alpha-gal syndrome."

The lone star tick is found in North Carolina, the Midwest and southern United States. In some cases, it can take months after the tick bite to start feeling sick after consuming meat.

"When I was first diagnosing patients with alpha-gal syndrome, it wasn't in the GI literature at all,"recalled McGill. "So these patients would come in and they'd have frequent abdominal pain and diarrhea -- symptoms of irritable bowel syndrome -- or recurrent nausea and vomiting. None of my patients associated their symptoms to meat."

About 75% of patients observed in a study recalled a tick bite, but ticks can be minuscule while in the larval stage so a bite might go unnoticed.

McGill recommends that symptomatic patients undergo a blood test called alpha-gal IgE. If positive, they should start an alpha-gal elimination diet.

Symptoms should resolve or significantly improve on the elimination diet, McGill said.

People with alpha-gal syndrome should avoid eating or drinking meat and milk products including butter, though symptoms can vary.

"Most people do fine with dairy,"said McGill. "On the other hand, I have had some patients who have reacted to even small amounts of mammalian byproducts in processed foods. I suspect the variability in tolerance has to do with your gut microbes at some level."

The lone star tick is most active between April and September. Someone who has previously been bitten and has alpha-gal should avoid additional tick bites because another bite could worsen their allergy, McGill noted.

Patients with symptoms like rashes, problems breathing or swelling of the face should be referred to an allergist, she added. Reactions may decrease with time, but repeat alpha-gal IgE testing could help determine a future treatment plan.

"It's important to get the word out,"McGill said. "There's so much GI illness without a clear cause found. GI doctors should consider this as a possible problem when seeing patients with these symptoms."

More information

The U.S. Centers for Disease Control and Prevention has more on alpha-gal syndrome.

SOURCE: University of North Carolina Health Care System, news release, March 21, 2023