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.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.