Ticks and tick-borne diseases are on the rise, and have been for years. While we usually think of Lyme disease when we think of ticks, there are plenty of other issues that can be caused by a tick bite, like Rocky Mountain spotted fever. Another, less well-known condition: mammalian meat allergy, which can result from a bite from a lone star tick.
What are lone star ticks and where do they live?
Lone star ticks once mainly lived in the southeastern U.S., but their range now includes the entire east coast and a big chunk of the midwest. Iowa is at the edge of the ticks’ range; Nebraska, Texas, and New York are all partly within its boundaries, according to this CDC map.
Thanks in part to climate change, ticks’ ranges are increasing, and they are more likely to survive the winter when the weather is warmer, making for larger tick populations each year. The ticks also piggyback, quite literally, on growing deer populations.
Lone star ticks are big for a tick, crawl quickly, and their bites hurt. This is in contrast to the blacklegged ticks of Lyme disease fame, which are smaller and whose bite you might not even notice.
All ticks feed by burying their head in your skin and sucking your blood until they fill up like a balloon. If you find a tick on you, remove it with tweezers or a tick-removal device. Do not burn its butt with a blown-out match; that actually increases the chance it can give you a disease.
Lone star ticks can also transmit ehrlichiosis, tularemia, heartland virus, and STARI. But by far the weirdest thing about them is their ability to cause a meat allergy.
How can a tick bite cause a meat allergy?
First of all, not every lone star tick bite causes the allergy. It’s completely normal to be bitten by a tick and not have any lasting consequences. But among people who have what’s called an alpha-gal allergy, most began to experience symptoms shortly after being bitten by a lone star tick.
There are other ticks that can cause this allergy, including one that is found in Europe and another in Australia. In the U.S., a meat allergy has so far only been linked to the lone star tick.
What is alpha-gal, and how can we be allergic to it?
The allergy is specifically to a compound called galactose-alpha-1,3-galactose, or alpha-gal for short. It’s a sugar, but you won’t find it in sweet foods like fruits. It is made by animals and attaches to proteins. Red meat, which is mainly protein, has small amounts of alpha-gal in it. (Not enough to register as sugar on the nutrition label; it’s a truly less-than-microscopic amount.)
Nearly all mammals make alpha-gal, and alpha-gal is found in their meat and milk, with one big exception: primates (like humans and monkeys) do not produce the substance. That means that our immune system may recognize alpha-gal as an invader.
Something about the bite of the lone star tick (and those of certain other ticks) can trigger our immune system to start attacking alpha-gal, and as meat from mammals contains alpha-gal—including beef, lamb, venison, and (though it’s not considered a red meat) pork—the result is an allergy to meat itself.
The exact mechanism that triggers the allergy isn’t entirely understood. One hypothesis is that ticks pick up proteins containing alpha-gal from other mammals they bite (like mice and deer) and then transfer them to us when they bite. But there’s also a possibility that tick saliva itself is the trigger.
What is it like to have an alpha-gal allergy?
The hallmark of alpha-gal allergy is that you sometimes get allergy symptoms like itching, swelling, and potentially anaphylaxis (which can be deadly) three to eight hours after eating meat. You may experience gastrointestinal symptoms as well, like diarrhea and stomach pain. Alpha-gal allergy is most common in people who spend a lot of time outdoors, like hunters and hikers, and often people remember suffering a painful tick bite before they started experiencing symptoms.
If you think you may have an alpha-gal allergy, bring it up with your doctor, and get a prescription for an epi-pen. Alpha-gal allergy is uncommon, and particularly if you don’t live in the southeastern U.S., your doctor may not think to test for it. People with alpha-gal allergy may find that they only have the reaction some of the time when they eat meat, but it can be severe when it happens, and anaphylaxis can be deadly.
Alpha-gal allergy can be diagnosed with the help of a blood test that looks for IgE antibodies against alpha-gal. (Skin prick tests, used for testing other types of allergies, can give a false negative. Mail order blood tests use a different type of antibody entirely, and are not reliable.)
While mammalian meat is the most common trigger, some people are sensitive enough that they need to avoid dairy (especially high-fat dairy, which contains more alpha-gal) and other animal products like gelatin. Some medical products can be an issue, too; the blood thinner heparin and the chemotherapy drug cetuximab contain alpha-gal. (If you’d like to read more, this paper contains recommendations for doctors and for people with alpha-gal allergy.)
While the allergy is considered to be lifelong, it can get better or worse over time. Getting another tick bite may temporarily make symptoms worse. Alcohol and exercise also seem to exacerbate symptoms. On the bright side, you can eat all the chicken, turkey, and fish you want.
How can I protect myself from lone star tick bites?
The same way you protect yourself against other tick bites:
- Check yourself for ticks after you’ve been outdoors. (At the very least, take a shower.)
- Consider coating your shoes and pants in permethrin, an insect-repelling spray that will last through several washings.
- Wear a good bug spray when you’re outdoors, especially on your ankles and legs.
If you are bitten by a tick, remove the tick with tweezers or a tick-removal device. Ask your doctor what to do next, since that decision is going to depend on where in the country you are, and what diseases or risks you face. There is no way to prevent an alpha-gal allergy if you’ve already been bitten, but other tick-borne diseases may be a possibility. Always seek medical care if you’re bitten by a tick and then get a fever or other symptoms.