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Meat Allergy From Ticks?

Researchers say bites from the lone star tick can cause alpha-gal syndrome (AGS), a potentially serious allergy to red meat

By Erin O'Donnell

For Sharon Forsyth of Washington, DC, it began with a hamburger. In the summer of 2019, Forsyth, then 56, ate a burger for lunch and about five hours later developed severe abdominal pain. She broke out in hives from head to toe, and the palms of her hands and soles of her feet swelled.

A tick with a white dot on its back. Next Avenue
Lone star ticks are named for the single white dot found on the backs of female ticks. They are concentrated in the southeastern states, the Mid-Atlantic region and New York.  |  Credit: Getty

The strange symptoms made Forsyth wonder. A friend had told her about a little-known condition called alpha-gal syndrome (AGS) just a few weeks earlier. He explained that it was an allergy to mammalian meat, including beef and pork, triggered by tick bites.

She needed to give up mammalian meat and medicines that contain alpha-gal, including dairy products, which made her feel "like I'd swallowed glass."

"I thought, 'Well, I just heard about this thing. I'm probably just imagining it,'" Forsyth recalled. She ate some spaghetti Bolognese made with beef and pork a short time later. She reacted again. And then she ate a hot dog and reacted a third time. This was not just her imagination.

Forsyth visited her doctor, who had never heard of AGS and initially ordered the wrong allergy tests. After some research, Forsyth found that the appropriate test was a blood test for alpha-gal IGE.

Her doctor ordered that test, which returned positive, confirming that Forsyth had indeed AGS and was allergic to mammalian meat. "It was very disruptive in my life, very difficult for me to eat out," she said. "I would react basically every time I did." Travel became especially tough. Forsyth began reading all she could about the alpha-gal syndrome and monitored her symptoms closely.

She realized that she needed to give up mammalian meat, foods and medicines that contain alpha-gal, including dairy products, which made her feel "like I'd swallowed glass," and gummy vitamins and pain reliever gel caps made with gelatin. She also had to avoid carrageenan, a seaweed-based ingredient.

What Causes Alpha-gal Syndrome?

Researchers have linked this condition to bites from the lone star tick in the United States. (The disease is associated with other tick types in other countries.) Lone star tick saliva contains a sugar molecule known as alpha-gal. 

Researchers have linked this condition to bites from the lone star tick in the United States.

Once the molecule enters the human bloodstream, some people develop an allergy to alpha-gal, which can take weeks or months to build. If an allergic person eats meat from mammals, including beef, lamb, pork, rabbit or venison, or consumes animal products, such as gelatin and dairy, they can experience various symptoms three to six hours later.

Some of these include hives and itchy rash, severe stomach pain and other gastrointestinal symptoms, joint pain, swelling of the mouth and throat, and even breathing difficulties or dangerously low blood pressure.

People with severe allergies can experience these symptoms simply from inhaling airborne particles from meat or dairy products as they cook.

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Where Are Lone Star Ticks Found?

Lone star ticks are named for the single white dot found on the backs of female ticks. They are concentrated in the southeastern states, the Mid-Atlantic region and New York, said Dr. Scott Commins, an allergist and immunologist with the University of North Carolina School of Medicine. 

Other hotspots include Arkansas, Oklahoma and Missouri, with some found in the Great Lakes region in Minnesota and Wisconsin. "The range of the lone star tick has expanded greatly over the past five to 10 years," Commins said.

These ticks are commonly found in and around forests with dense undergrowth. They move quickly and are known to be aggressive in seeking out humans. "Some people say they're like a cross between a pack of wolves and lentils," Forsyth said, "like a pack of hungry lentils coming after you."

In the months before her diagnosis, Forsyth, an avid conservationist, had been hiking through fields with a friend, looking for rare butterflies. "I remember that I got maybe five tick bites within two weeks," Forsyth recalled.

How Common Is Alpha-gal Syndrome? 

A July 2023 study from the Centers for Disease Control and Prevention (CDC) reported that the number of cases of AGS has "increased substantially" since 2010. Researchers estimated that as many as 450,000 people in the United States may have developed this condition.

"It really seems like we have more work to do, raising awareness and teaching providers about how to manage it."

But many physicians don't know about AGS. Another CDC study surveyed health care practitioners around the United States and found that nearly half had never heard of it. As a result, patients may search for years before they are diagnosed.

"It really seems like we have more work to do, raising awareness and teaching providers about how to manage it," said Commins, a coauthor on both studies.

Interestingly, once Forsyth was diagnosed, her husband, Adrian, 68, began to wonder if AGS could be the cause of his chronic digestive problems. Testing revealed that he had it too. His digestion improved once he gave up mammalian meat, dairy and other alpha-gal products, and his severe arthritis also resolved. 

A biologist, Adrian had received many tick bites while researching dry forests in Latin America. "He likely had it for decades before being diagnosed," Forsyth said.

How Is Alpha-gal Syndrome Diagnosed?

If patients have symptoms, that often develop in the middle of the night after eating mammalian meat, they should ask their doctor for an alpha-gal IGE blood test, Commins said.

But he advises against testing for alpha-gal IGE if a person knows they've received a tick bite but don't have allergy symptoms. "We really like the symptoms to guide the testing," he said because it's possible to be positive for alpha-gal IGE but not be allergic to mammalian meat.

How Is Alpha-gal Syndrome Managed?

There is currently no cure for AGS. People with AGS should carry an epinephrine autoinjector, such as an EpiPen, in case of anaphylaxis, and stop eating mammalian meat, Commins said. He added that some (but not all) patients also react to dairy and gelatin, so some experimentation with diet may be necessary.

After her diagnosis, Forsyth began collecting research-based information about AGS and created the Alpha-gal Information website. It includes information about medicines and medical products that contain alpha-gal. For example, surgical sutures can be made with mammal-derived collagen.

"We really like the symptoms to guide the testing."

Commins said that one of the most critical steps is avoiding future tick bites. In some cases, the allergy will wane after three to five years; Commins periodically gives his patients the alpha-gal IGE blood test to determine if they can safely consume alpha-gal-containing foods again. 

But this outcome is less likely for people living where lone star ticks are common. "For a lot of folks who work outside or play outside, it's really tough for the allergy to go away because they just keep getting bites," Commins said.

How Can I Avoid Lone Star Tick Bites?

The CDC recommends treating clothing and gear, including hiking boots, with insect-repellent permethrin. Wearing white clothing (which makes ticks more visible) and tucking pants into socks and boots can also help. Check your body for ticks after being outdoors.

Forsyth and her husband continue to hike regularly. But they are cautious. In addition to wearing permethrin-treated clothing and shoes, they use a lint roller to roll them after hikes. 

They also put double-sided carpet tape on their boots; they've found that ticks get trapped on the tape and can't bite. "We've had over a dozen ticks on us this year," Forsyth said, "but we haven't had any tick bites."

Erin O'Donnell
Erin O'Donnell Journalist Erin O’Donnell covers health, science, and parenting topics. Her work has appeared in WebMD, Cancer Today Magazine, and Harvard Magazine, among many others.

She lives with her husband and sons in Milwaukee, Wisconsin, and loves walking along Lake Michigan. For more of her work, visit http://erinodonnell.net/ or find her on Twitter @ErinODWriter.
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