Tick bites can cause all sorts of nasty afflictions. And if you're bitten by a Lone Star tick, here's one more to add to the list: a red meat allergy.
Laura Stirling, 51, a Realtor who lives in Severna Park, Md., was diagnosed with the allergy last year. She got a tick bite while walking on a trail with her dog, Gunner, near her home.
"I found [the tick] 3 or 4 inches to the left of my hip bone," Stirling recalls. At the time, she say, she didn't think much of it. "I just took it off and threw it away."
Then, three weeks later, after she ate an Italian-style pork sausage for dinner, she had a horrible reaction. The reaction began about six hours after her meal, which is typical of this allergy.
"It was the middle of the night. I woke up covered in hives," Stirling recalls. She woke her husband with all her itching and scratching. She felt lightheaded, and she experienced stomachaches and other gastrointestinal troubles.
An allergist gave her a blood test to check for an alpha-gal meat allergy. When the test came back positive, she was told to avoid all red meat, including beef, pork and lamb. (Despite a long-running campaign marketing it as "The Other White Meat," pork is classified as a red meat.) Some people who develop the allergy can no longer tolerate dairy products.
Stirling was surprised when she first got the news. "I thought it was completely crazy, because I've eaten dairy and red meat all my life," she says. But she quickly realized the diagnosis was spot on. Meat and dairy did trigger her symptoms.
"Her story is really interesting," says Dr. Scott Commins, an allergist and associate professor of medicine at the University of North Carolina, Chapel Hill. He says it is a meat allergy, but about 15 to 20 percent of patients with the alpha-gal allergy also report getting symptoms from dairy, especially high-fat dairy such as ice cream.
About 10 years ago, Commins was among the first physicians to identify the allergy in patients with tick bites. Back then, there were just a few dozen known cases.
That has increased dramatically. "We're confident the number is over 5,000 [cases], and that's in the U.S. alone," Commins says. There are also cases in Sweden, Germany and Australia — likely linked to other species of ticks.
In the U.S., the Lone Star tick has expanded its range beyond the Southeast, and there are documented cases of alpha gal meat allergies farther north — including New York, Maine and Minnesota.
"The range of the tick is expanding," says Commins. So is awareness about the red meat allergy it can cause. "We have a blood test, and the word is getting out."
Commins first began trying to solve the mystery of what was causing a red meat allergy in 2007, when he was at a University of Virginia allergy clinic. "We had a growing population of people reporting these reactions [to meat]," he recalls.
Early on, ticks were not on his radar. "We thought it was a parasite," Commins explains. But then he and his colleagues realized that many of the patients were outdoorsy types who spent time hiking. And eventually they pieced together the tick bite connection.
One hint came from mapping newfound cases of the meat allergy. When he compared that with the geographic distribution of Rocky Mountain spotted fever, also caused by the Lone Star tick, he saw striking similarities. "That map overlapped very nicely with the states where we were finding these emerging reactions to beef, pork and lamb," he says.
There's still a lot to learn about the alpha-gal allergy. Alpha gal is a sugar that animals — including cows, pigs and lamb — make in their bodies. "As humans, we don't make this alpha gal sugar," Commins explains. "We all make an immune response to it." So, how does a tick bite cause the allergy?
It's possible that ticks inject humans with alpha gal when they bite. The ticks likely get it from feeding off wild animals, such as mice or squirrels, that also carry alpha gal. Or it's possible that ticks activate the response in another way.
"Whatever the tick is doing, it seems that it's a very potent awakener for our immune system to produce antibodies, "Commins says. "And in this case, it's antibodies to this very particular sugar in red meat."
Laura Stirling now avoids all red meat and dairy. "As soon as I stopped, I was fine, I felt great," she says.
"I get enough poultry and seafood in my diet," she says, so she's not pining for beef. And with all the nondairy options now available, she says it's not hard to avoid milk. "But I kind of miss having, you know, a bowl of ice cream or really good cheese."
She looks forward to the day when she may be able to eat foods such as prosciutto and salami — and ice cream — again. And there's a good chance she will outgrow the allergy.
"It can resolve," Commins says. But he adds a caveat: "We need people to avoid additional tick bites for the allergic response to wane." For people who like to be outside, this can present a challenge.
"I wear bug spray and I'm very cautious," Stirling says.
STEVE INSKEEP, HOST:
Here's a surprising side effect of being bitten by a tick - tick bites can cause many diseases. And if you're bitten by a lone star tick, you could develop a food allergy. This problem is spreading as the tick's range expands. NPR's Allison Aubrey reports.
ALLISON AUBREY, BYLINE: One day last summer, Laura Stirling took her dog Gunner for a walk on a trail near her house. She lives in Severna Park, Md. Later that evening, she realized she'd bitten by a tick.
LAURA STIRLING: I found it 3 or 4 inches to the left of my hip bone and didn't think anything of it. I just took it off and threw it away.
AUBREY: But about three weeks later, she ate an Italian-style pork sausage for dinner and had a horrible reaction.
STIRLING: I would say it was probably six hours after I ate it. It was in the middle of the night. And I woke up covered in hives.
AUBREY: She was itching and scratching. She felt lightheaded. She also noticed stomach aches. So she went to see an allergist.
STIRLING: He asked me, did you change your detergent? Did you change anything in your diet? And I said no. And he said, in the last month, were you bitten by a tick? And I said yes.
AUBREY: After a blood test, the allergist told her she was allergic to red meat and maybe dairy, too.
STIRLING: I thought it was completely crazy because I've eaten dairy and I've eaten red meat all my life.
AUBREY: Her story is pretty typical of people who develop a red meat allergy after a tick bite, says allergist Scott Commins. He's an associate professor at UNC Chapel Hill. And he was among the first to identify the allergy in patients with tick bites about 10 years ago. He says back then, there were just a few dozen known cases. But now...
SCOTT COMMINS: We're confident that the number is over 5,000 at least in the U.S. alone.
AUBREY: There are also cases in Sweden, Germany and Australia likely linked to other species of ticks. Now, Commins says in the U.S., cases have moved beyond the southeast to New York, Maine and Minnesota.
COMMINS: Absolutely we're going to find that this continues to expand. The reach of the tick is expanding. And equally, I think, we have a blood test, we're raising awareness, and the word is getting out.
AUBREY: There's still a lot to learn about this allergy. It's known as an alpha-gal allergy. Alpha-gal's a sugar that animals make, including cows and pigs, but we don't.
COMMINS: As humans, we don't make this alpha-gal sugar. We all make an immune response to it.
AUBREY: So how does a tick bite cause the allergy? Well, it's possible that ticks inject alpha-gal into people's bodies when they bite. The ticks likely get it from feeding off wild animals such as mice or squirrels. Commins says it's also possible that ticks activate the response in another way.
COMMINS: Whatever the tick is doing, it seems that it's a very potent awakener for our immune system to produce antibodies. And in this case, it is antibodies to a very particular sugar in red meat.
AUBREY: As for Laura Stirling, she now avoids all dairy and all red meat.
STIRLING: Once I was told just stop eating it, I was fine. I felt great.
AUBREY: Allergists usually give their alpha-gal patients epi pens because reactions can be dangerous. But the good news is that people can outgrow the allergy. This is most likely to happen if they avoid further tick bites. Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.