Imagine eating a burger for dinner and waking up at midnight covered in hives, with no idea why. For hundreds of thousands of Americans, the cause turns out to be a tick bite. The condition is called alpha-gal syndrome, and the tick most often linked to it is the lone star tick. Here's what you should know.
What is alpha-gal syndrome?
Alpha-gal syndrome (AGS) is what the CDC calls "a serious, potentially life-threatening allergy and tickborne disease." It's an allergy to alpha-gal, a sugar molecule found in the bodies of most mammals, but not in people.
That's why it's often called a "red meat allergy." People with AGS can react to beef, pork, lamb, venison and rabbit, and some also react to dairy products and to certain medications and other products made from mammals.
How can a tick bite cause a meat allergy?
According to the CDC, a tick bite can transfer alpha-gal into a person's body. In some people, the immune system then flags alpha-gal as a threat. The next time they eat red meat or are exposed to other mammal products, their body reacts with an allergic response.
So unlike Lyme disease, AGS isn't an infection. It's an allergy your body develops after the bite.
Why the lone star tick?
The CDC says the lone star tick is most often associated with alpha-gal syndrome. A few cases have also been reported after bites from blacklegged (deer) ticks and western blacklegged ticks.
The lone star tick is easy to recognize once you know what to look for: it's reddish-brown, and adult females have a single white dot, the "lone star," on the back. The CDC describes it as "a very aggressive tick that bites humans," and it's widely distributed across the Northeast, South and Midwest. For a side-by-side comparison, see Deer Tick, Lone Star Tick or Dog Tick? How to Tell Them Apart.
Alpha-gal syndrome symptoms
One of the strangest things about AGS is the timing. The CDC says symptoms usually appear 2 to 6 hours after eating red meat or dairy, not right away like many food allergies. That delay is one reason it's often missed. Symptoms can include:
- Hives or an itchy rash
- Nausea, vomiting, diarrhea, heartburn or severe stomach pain
- Cough, shortness of breath or difficulty breathing
- Swelling of the lips, throat, tongue or eyelids
- Dizziness, faintness or a drop in blood pressure
- Anaphylaxis, a severe combination of symptoms
If you're having a severe allergic reaction or anaphylaxis, get emergency care immediately.
How common is it?
More common than most people think:
- More than 110,000 suspected cases were identified in the US between 2010 and 2022, and the CDC estimates as many as 450,000 people may be affected.
- In a CDC survey of 1,500 healthcare providers, nearly half had never heard of AGS, and only 5% felt very confident diagnosing and managing it.
- The highest rates of suspected cases cluster across parts of the South, Midwest and Mid-Atlantic, including Oklahoma, Arkansas, Missouri, Tennessee, Kentucky, North Carolina and Virginia. Suffolk County, New York, on Long Island, reported the most suspected cases of any county from 2017 to 2022.
A July 2026 CDC report added another twist. Testing blood donor samples from 10 states, researchers found alpha-gal antibodies in about 31% of samples from Arkansas and 26% from Missouri, compared with about 1% in Washington. Having these antibodies isn't the same as having AGS, and the authors stressed that testing should be reserved for people with symptoms. But it shows how widespread exposure is where lone star ticks live.
How is alpha-gal syndrome diagnosed?
A healthcare provider will look at your history and symptoms, do a physical exam, and may order a blood test for antibodies to alpha-gal. If you've had unexplained reactions hours after eating meat, especially after time outdoors in lone star tick country, bring it up with your doctor. It may help to mention AGS by name.
How to protect yourself
The CDC puts it simply: the best way to protect yourself and your family from AGS is to prevent tick bites.
- Use an EPA-registered repellent, and treat clothing and gear with 0.5% permethrin.
- Walk in the center of trails, and check yourself, your kids and your pets after being outside.
- Remove any tick you find right away with fine-tipped tweezers. Here's how to remove a tick the right way.
- Save the tick in a sealed vial and note the date and place. If symptoms show up later, you'll be able to tell your doctor exactly which tick bit you.
Heading outdoors? Our tick prevention checklist for hiking and camping covers the rest.
Know your tick
With alpha-gal syndrome, knowing whether you were bitten by a lone star tick is useful information for your doctor. The Tick-Away tick removal kit includes a tick ID card showing the lone star tick, deer tick and American dog tick, plus a magnifier to spot that telltale white dot and a sealed vial to keep the tick. It also has fine-point tweezers and a notched remover, all in a zip case that clips to your pack. Get your Tick-Away kit.
This article is general information, not medical advice. If you think you may have alpha-gal syndrome, talk to a healthcare provider. Sources: CDC, About Alpha-gal Syndrome; CDC, Signs and Symptoms of AGS; CDC, Emerging Tick Bite-Associated Meat Allergy; CDC MMWR, Geographic Distribution of Suspected AGS Cases; CDC MMWR, Alpha-gal IgE Seroprevalence (2026).
