A potentially life-threatening allergy to red meat may impact almost half a million Americans, but many doctors have no idea what it is or how to treat it, according to research published Thursday.
Two reports from the Centers for Disease Control and Prevention reveal significant gaps in knowledge about alpha-gal syndrome, even as the condition is rising in the population.
"Patients are out there, but the primary care folks, the health care providers, just don't seem to know about it," said Dr. Scott Commins, an allergy immunology specialist at the University of North Carolina Department of Medicine in Chapel Hill, and a co- author of both reports.
Alpha-gal syndrome is a tick-borne illness that leads to allergic reactions from eating red meat, including meat of cows, deer, pigs or goats. Some people also develop allergies to dairy and other byproducts from processing those animals, like gelatin.
What are symptoms of alpha-gal syndrome?
Symptoms of alpha-gal syndrome can be wide-ranging, including:
- Nausea.
- Stomach cramps.
- Diarrhea.
- Often, people will become itchy and develop hives. They may be short of breath and even develop anaphylaxis in extreme cases.
Unlike other food allergies, hives, itching and other typical reactions are not immediate. Symptoms usually don't pop up until hours after eating meat because of how slowly the body digests it. That makes it difficult to diagnose, and is one reason the syndrome continues to fly under the radar of many doctors.
In one of the new reports, 42% of 1,500 doctors surveyed had never heard of alpha-gal syndrome. A further 35% said they were not confident in their ability to detect or treat the illness.
The doctors in the survey were mostly primary care providers who did not specialize in allergies. But it's these doctors to whom patients usually turn to first when they have unusual symptoms. If they aren't thinking of alpha-gal syndrome, a diagnosis can be delayed for years, experts said.
"That complicates our understanding of the true number of cases," said Ann Carpenter, a CDC epidemiologist and co-author of the new reports.
A second report found that cases of alpha-gal syndrome are rising. From 2017 through 2021, the CDC said, the number of new cases increased by about 15,000 each year.
Dr. Erin McGintee, an allergy and immunology physician in private practice on Long Island, New York, said she has noted the increase in patients since she began seeing alpha-gal syndrome more than a decade ago. Since then, she has treated roughly 900 such patients.
"Out here in the Hamptons," she said, "most people know at least one other person who has the syndrome."
Nationwide, more than 110,000 cases have been detected since 2010, the CDC said. But that may be a vast underestimate.
The agency suspects that the number of people affected may be as many as 450,000.
What is alpha-gal syndrome?
The blood of cows, deer, goats and pigs contains a specific sugar molecule called alpha-gal. It is not found in humans, fish or birds.
When ticks, usually the lone star tick, feed on those mammals, the alpha-gal gets into their saliva. Alpha-gal can then be transmitted to people through a tick bite.
When that happens, the body recognizes alpha-gal as a foreign invader, producing antibodies that prompt the immune system to become allergic to it. Subsequently, an infected person can become quite sick after consuming something that contains alpha-gal.
"The prototypical scenario is someone who tends to wake up in the middle of the night with itching or hives, and then that will tend to progress to gastrointestinal distress, abdominal cramping and diarrhea," Commins said.
That's exactly how Debbie Nichols, 44, of Blacksburg, Virginia, first suspected that eating red meat was triggering her ongoing health problems.
She woke up in the middle of the night with severe abdominal pain after eating a steak dinner. "I got in the shower because it was all I could think to do to try to minimize the pain in my belly," she said.
Nichols had experienced similar pain and gastrointestinal symptoms since about 2007 without any obvious cause.
"I spent years trying to convince doctors that there was something wrong with me, and they were telling me 'No, you look good, you're healthy,'" she said. It wasn't until 2019 that a blood test diagnosed her with alpha-gal syndrome.
She has since cut all mammal products from her diet.
"My life changed with my alpha-gal diagnosis," she said. "I feel a million times better."
The syndrome is a relatively new discovery, first revealed not by allergic reactions to meat, but from a cancer drug.
The Food and Drug Administration approved a monoclonal antibody called cetuximab in 2006 to treat head and neck cancers, and later to treat colon cancer.
"When that drug was licensed and went on sale, it became obvious that there was a real problem," said Dr. Thomas Platts-Mills, head of the division of allergy and clinical immunology at the University of Virginia.
The drug was causing allergic reactions in patients "that didn't make any sense," he said, because they were only occurring in certain parts of the country.
"They weren't happening in the North, in New York or Chicago," Platts-Mills said. The only cases at the time were reported in the Southeast, primarily in Arkansas, North Carolina, Tennessee and Virginia. The problem had to be connected somehow with the environment in which people were living, he said.
When Platts-Mills and a team of researchers studied the blood from these patients before they were treated with cetuximab, they found antibodies to a sugar molecule, galactose-alpha-1,3-galactose, now commonly known as alpha-gal.
The team knew that the sugar molecule — which was used in manufacturing cetuximab — came from certain animals, such as cows, deer, goats and pigs. And patients themselves backed up the association.
"We had patients coming in saying, 'I get anaphylaxis after eating beef, pork or lamb, but not after chicken, turkey or fish,'" Platts-Mills said.
"We proved beyond doubt that the patients had antibodies to this molecule before they got treated" with cetuximab, he said.
Further research led the team to link the problem to a bite from the lone star tick, prevalent in the Southeast where the cancer drug-related cases were occurring. Since then, the lone star tick has spread farther into the Northeast and the Midwest.
The landmark findings were published in the New England Journal of Medicine in 2008.
Fifteen years later, researchers are still working to understand the complexities of alpha-gal syndrome. Why do some people who test positive for the antibodies get sick after eating meat, but others don't? Why do some people also develop sensitivities to dairy and byproducts of meat?
The good news, McGintee said, is that the syndrome is manageable with lifestyle changes.
"For the most part, if patients avoid the alpha-gal containing foods, they should be able to lead a completely normal life," she said.
Nichols, an avid home cook, has also had to cut out dairy, and was nervous at first about making significant changes to her diet. That's all changed.
"People say all the time, "'I don't know how you do it. I couldn't live if I couldn't have steak,'" she said. "My thought is, well you don't know how bad I felt before I gave it up and how good I feel now."
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