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Mystery Allergy Strikes Adults

Is meat the new pollen?

red meat allergy

— Tobias Regell/Gallery Stock

When Linda Quinn awoke in the middle of the night in a Tulsa, Okla., motel room last July, a thousand miles from home, her first thought was, "Not again."

Huge itchy red blotches blanketed her torso. A great weight seemed to be pressing on her chest, pushing air out of her lungs. She felt dizzy, a sure sign of plummeting blood pressure and a hallmark of anaphylaxis—the potentially fatal allergic reaction that had sent her to the emergency room half a dozen times since 2006. She quickly roused her husband, Joseph, who called the front desk. A clerk summoned an ambulance, and Quinn was whisked to a nearby emergency room.

Both Quinns were baffled: Linda hadn't eaten any of the foods doctors warned her to avoid, after being diagnosed with a food allergy. Only later would the retired couple discover that the culprit was something neither had imagined.

Linda Quinn's diagnosis, shared by a growing number of patients around the world, is upending long-held views of food allergies, which held that adults don't tend to develop allergies late in life. And yet these adults, some as old as 80, suddenly developed an allergy that sounded downright bizarre: They were allergic to meat.

A pair of recent studies—one published by a team from the University of Virginia School of Medicine, where Quinn was later treated, and another in Sydney, Australia—are prompting doctors to reconsider the prevalence of this allergy that has been considered rare and to consider a likely trigger that was previously unknown.

"It's really interesting, because it's so unexpected," said physician Wayne Shreffler, director of the Food Allergy Center at Massachusetts General Hospital in Boston.

Saju Eapen, M.D., an allergist in private practice in Roanoke, Va., agrees. Eapen, who calls the finding "transformational," said that he and his partners have referred nearly 150 patients to U.Va. for specialized testing in the past year. "This was not something we looked for in the past."

Unexplained episodes

For Linda Quinn, 61, a former veterinary technician, life in rural Farmville, Va., was just what she and her husband, a former housing inspector, had dreamed of when they left the suburbs of Washington, D.C. They had a horse, a cat, dogs and, they soon learned, a whole lot of ticks.

While the speck-size insects ignored Joe, they gravitated to Quinn, who grew used to plucking the "voracious little buggers" off her clothing or exposed skin after a walk or trip to the barn. She also got used to the inevitable reaction a few hours after a tick bite, when the bite would become swollen and ferociously itchy. But the symptoms always subsided.

In 2006 Quinn began experiencing frightening episodes that seemed related to visits to the barn. At first she thought it might be a reaction to hay or mold. Giant itchy red hives would suddenly appear from her neck to her knees. Sometimes she would have difficulty breathing and would become dizzy, her normally high blood pressure once plummeting as dangerously low as 86/60.

Neither Quinn nor her doctor had any idea what was causing these episodes. Doctors would give her epinephrine and Benadryl to counteract the symptoms, wait for them to subside, then send her home. After several months it became clear that the episodes were becoming more violent and more frequent.

Doctors had no idea what was causing her anaphylaxis. Her doctor told her she needed to always carry an EpiPen, a device that administers an emergency epinephrine injection. In November 2007 he referred her to the University of Virginia's allergy clinic in Charlottesville, headed by Thomas Platts-Mills, M.D., an internationally prominent allergist, for further evaluation.

I think you've got it!

After taking an extensive history, Platts-Mills and his team performed skin tests and discovered something that stunned Quinn: She was highly allergic to beef, as well as pork and lamb. The allergy, which typically surfaces in childhood, is considered rare.

Platts-Mills asked if she ate meat. Every day, she replied.

Had she recently been bitten by ticks and developed a reaction? After Quinn recounted her frequent bites and the inevitable itchy swelling, Platts-Mills shed his British reserve.

"I think you've got it! You've got the real thing!" he told her.

Quinn soon learned that his lab was working on a novel new theory: that an uncommon reaction to tick bites can trigger the development of a sudden allergy to meat in adults like Quinn who have eaten meat for decades without incident. She quickly agreed to join Platts-Mills' study, becoming Patient 15. Several hundred people are now enrolled.

Long-held views upended

Last year, the Virginia team published a study in the Journal of Allergy and Clinical Immunology detailing the cases of 24 adults, including Quinn, who had developed a sudden meat allergy. Eighty percent reported being bitten by ticks weeks or months before the allergy appeared. Many had experienced anaphylaxis as much as six hours after eating red meat, a highly unusual occurrence because food allergies typically cause violent reactions in less than 30 minutes. Similar findings were reported in the Medical Journal of Australia by a team of Sydney allergists.

So how does a tick bite trigger a sudden allergy to meat? Scott Commins, an assistant professor of medicine and lead author of the U.Va. study, said that in susceptible people such as Quinn, a tick bite that causes a significant skin reaction seems to trigger the production of an antibody that binds to a sugar present on meat known as alpha-gal.

When a person who has the antibody eats meat, that triggers the release of histamine, which causes the allergic symptoms: hives, itching and, in the worst case, anaphylaxis.

But many questions remain and are the subject of ongoing research, said Platts-Mills, who has the problem himself. (An avid hiker, he suffered numerous bites from ticks that had nested in his hiking boots.) His lab has collected data on more than 300 patients from the United States and abroad and has become a referral center for suspected cases.

"We're sure ticks can do this," he said. "We're not sure they're the only cause." Nor do researchers know why anaphylaxis is so delayed or why only some people develop a problem after tick bites. They do know that the allergic reaction is dose-related. Eating a small amount of meat probably won't cause a serious problem; a large steak will. Attacks can be unpredictable and don't occur every time a susceptible person eats red meat.

Commins said researchers have also observed that people with certain blood types appear to be more at risk. Those with the rarest types—B and AB—do not appear vulnerable, because elements in their blood are chemically similar to alpha-gal.

Climate also appears to play a role: Blood samples from Boston and northern Sweden almost never reveal alpha-gal antibodies, which are common in samples from patients in Virginia, North Carolina and other Southern states, as well as in southern Sweden and parts of Australia—all areas that do not experience hard freezes that kill ticks.

In Quinn's case, testing revealed that she had type A blood and exceptionally high levels of the antibody to alpha-gal. Because there is no treatment for the allergy, she cannot do much except to avoid beef, lamb and pork—or anything cooked with them.

Remember that episode in Tulsa? Quinn later discovered that the steak fries she had eaten at dinner had been prepared in oil previously used to fry beef.

She said she now asks about how a food is prepared when she eats out, and is trying to adjust to life without her favorite food.

"This changes your life tremendously," she said. "I'd love a good steak."

Sandra G. Boodman writes about medicine and health for the Washington Post and Kaiser Health News.