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A Lone Star Tick on a leaf. Credit Judy Gallagher

An eight-legged brown creature about a quarter inch in size could make you want to skip out on your next cheeseburger.

Found in North Carolina, the Midwest and Southern U.S., the Lone Star Tick can transmit the alpha-gal sugar, a sugar present in all mammals except humans, into the blood through its bite. This causes some to become allergic to mammalian (mammal) meat. These ticks will be on the prowl for their next host in the coming weeks.

“The allergy can cause recurrent abdominal pains, diarrhea, or vomiting, without more obvious allergic symptoms like rash or swelling,” explained Sarah McGill, MD, Msc, an associate professor in the Division of Gastroenterology and Hepatology.

Sarah McGill, MD, Msc

Dr. McGill has been studying Alpha-gal syndrome for over eight years. She, along with UNC Allergist Scott Commins, MD, PhD, and Internist Michael Croglio, MD, were the first to describe the condition in gastroenterology (GI) patients. Dr. McGill has now published a national clinical practice update for gastroenterologists and other clinicians to follow.

“We want the update to raise awareness. 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,” Dr. McGill said.


In addition to presenting with common symptoms, the reaction doesn’t occur until hours after someone consumes meat, making it difficult to pinpoint the correct cause. Furthermore, there can be months in between a person getting bit by the tick and when they first begin feeling sick after a meal.

“When I was first diagnosing patients with Alpha-gal syndrome, it wasn’t in the GI literature at all. 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,” recalled Dr. McGill.

Among the patients Drs. McGill, Commins and Croglio observed in a study, 75% recalled a tick bite. However, the Lone Star Tick can bite in the larval stage when it is only 0.5 mm to 1 mm long. Dr. McGill recommends symptomatic patients undergo a blood test called Alpha-gal IgE and if positive, start an alpha-gal elimination diet. Among patients with GI manifestation of the allergy, symptoms should resolve or significantly improve on the elimination diet.


The alpha-gal sugar is present in mammalian meat and any products made from mammals such as lard, milk, butter, etc. People with alpha-gal syndrome should avoid eating or drinking these foods. However, tolerance varies.

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

The Lone Star Tick is most active April through September. It is advised alpha-gal-allergic individuals try to avoid additional tick bites because this may worsen the allergy. If a patient has symptoms like rashes, problems breathing or swelling of the face they should be referred to an allergist. Reactions may also decrease with time and repeat alpha-gal IgE testing could be helpful in determining a future treatment plan.

“It’s important to get the word out. 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,” Dr. McGill said.

Jana G. Hashash, MD, MS, from the Mayo Clinic in Florida and Thomas A. Platts-Mills, MD, at the University of Virginia were co-authors of the Alpha-gal syndrome update for the GI clinician.