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What is alpha-gal allergy? Tick bites are causing more people to become allergic to red meat

Hours after eating red meat, people with the allergy can experience hives, redness, itching, swelling and intense gastrointestinal distress.
/ Source: TODAY

This summer, be especially vigilant about a tiny menace that could spoil your appetite for years.

A bite from the lone star tick — “a very aggressive tick that bites humans,” as the Centers for Disease Control and Prevention describes it — can lead people to develop an allergy to red meat and, in some cases, dairy.

Kristie Downen of Springfield, Missouri, was one of the people diagnosed in 2019.

"Food started hurting. It got to the point where my stomach would swell up, I was vomiting," Downen told NBC affiliate KY3 last week. "It's still unbelievable that a tick would make you allergic to food."

Experts who have been monitoring the strange sensitivity, known as an alpha-gal allergy, for years say the number of people affected just keeps rising. One recent study warned its prevalence has been increasing "drastically."

There are now more than 5,000 known cases of the allergy in the U.S. alone, said Dr. Scott Commins, an allergist and associate professor at the University of North Carolina at Chapel Hill School of Medicine.

That’s up from 3,500 cases just three years ago. Doctors at Commins’ allergy clinic now see 12-15 new patients with the allergy a week, he said. Based on unpublished estimates among allergists, there are approximately 10,000 cases worldwide as of 2019, Commins added. The rising numbers continue to worry him.

“It does seem like it’s really growing,” Commins, who was one of the first doctors to study the allergy, told TODAY.

“It appears the range of this tick is expanding… I also think it’s driven by folks are just encouraged to go outside more and perhaps they have more tick bites.”

It’s part of an overall trend. The number of reported tickborne diseases more than doubled from 2004 through 2016, the CDC reported last year. During that period, seven new germs that spread through tick bites were discovered in the U.S. At the same time, ticks and the germs they spread were growing in number and moving into new areas, the agency noted.

In 2017, the most recent year for which statistics were available, health departments reported a record number of cases of tickborne disease to the CDC.

The lone star tick is widespread in the southeastern and eastern U.S., and is now being found as far north as Maine, Wisconsin and Canada. A crowdsourced map is keeping track of alpha-gal allergy cases worldwide.

This map shows the extent of established Amblyomma americanum tick populations, commonly known as lone star ticks. But tick abundance within this area varies locally and the map does not represent the risk of contracting any specific tickborne illness, the CDC says.CDC

One reason may be the explosion of the deer population on the East coast, said Dr. Thomas Platts-Mills, who heads the division of allergy and clinical immunology at the University of Virginia and who helped discover the link between the lone star tick and the allergy.

A deer can carry 500 ticks — primarily lone star ticks, he said.

“This is a very odd situation: most ticks are specific for some animal, so there are dog ticks, pig ticks, cattle ticks — these ticks really don’t like humans much. But the lone star tick really does like humans,” Platts-Mills said. “We’ve got deer on the lawns and they’re dropping these ticks everywhere.”

The alpha-gal allergy is named after a sugar found in animals. Humans don’t have alpha-gal, but make an immune response to it. As TODAY first reported in 2016, it’s believed the lone star tick picks up alpha-gal after biting a deer, then transfers it into a person’s bloodstream when it bites a human. When a person is sensitized to alpha-gal, it triggers an allergic reaction. A blood test can confirm the allergy.

Researchers recently linked this sensitivity to the buildup of plaque in heart arteries, boosting the risk of heart attacks and stroke for people who have the allergy.

Platts-Mills has the allergy himself: he was bitten in August 2007 and experienced his first reaction that November hours after eating lamb chops. The delayed response can make it a challenge for doctors and patients to connect the foods with symptoms, the American College of Allergy, Asthma & Immunology noted.

“One of the fascinating things, the hallmark of this, is that the symptoms occur in a delayed fashion, three to six hours after someone typically eats red meat,” Commins said.

The symptoms can include hives, redness, itching and swelling. Some patients complain of intense gastrointestinal distress, like abdominal cramping and pain, Commins said. People can end up with anaphylaxis, a life-threatening allergic reaction that requires emergency treatment, he added. Most of his patients carry Epi pens.

The allergy involves red meat like beef, pork or lamb; and, in some cases, dairy — especially heavy-fat dairy like ice cream. Doctors aren't sure whether it only takes one lone star tick bite or several for people to develop the sensitivity, but anyone, including children, can develop it, Commins said.

The treatment is avoidance, so patients are limited to eating meat from fish, chicken and turkey.

“If it swims or flies, it’s fine,” Commins said.

“If you’re my age, you’ve got a cardiologist who’s been telling you the treatment already, and that is avoid red meat completely, and don’t eat full-fat milk and cheese,” Platts-Mills, 77, said.

The allergy usually goes away after two to three years as long as the patient has no additional tick bites. Doctors are working on a vaccine, but that’s likely several years away.

To avoid tick bites, experts offer these suggestions:

  • Stick to marked trails and walk in their center. Ticks live in grassy, brushy or wooded areas, so you want to avoid brushing up against thick vegetation.
  • Use tick repellents.
  • Perform tick checks on your clothes and body after you’ve been outside. When it comes to lone star ticks, the adult female has a white dot on her back.
  • Shower within two hours of coming indoors.
  • If you get a tick bite, remove the tick and monitor yourself for any symptoms.
  • If you notice any concerning symptoms after eating red meat, get the alpha-gal allergy blood test.

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