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Alpha-Gal Syndrome: The Tick Bite That Can Make You Allergic to Red Meat

Alpha-gal syndrome is a serious, potentially life-threatening allergy that can develop after a tick bite. Alpha-gal is a molecule found in most mammals but not in people. Once the immune system flags it as a threat, eating red meat or other products made from mammals can trigger a reaction, usually two to six hours later.

What is alpha-gal syndrome?

Alpha-gal syndrome, usually shortened to AGS, is a tickborne disease that shows up as an allergy rather than an infection. Alpha-gal is a molecule, galactose-alpha-1,3-galactose, that the CDC describes as naturally produced in the bodies of most mammals but not in people. It is also found in the saliva of some ticks.

When a tick bites, it can transfer alpha-gal from its saliva into a person's blood. The immune system can identify alpha-gal as a threat and trigger an allergic reaction. From then on, symptoms occur after the person eats red meat or is exposed to other products made from mammals. Hence the other names for AGS: red meat allergy, or tick bite meat allergy.

CDC researchers writing in MMWR characterize AGS as an immunoglobulin E (IgE) mediated hypersensitivity to alpha-gal, an oligosaccharide found in most nonprimate mammalian tissue and in products derived from those mammals, including milk, other dairy products, and some pharmaceutical products. As of that 2023 report, no treatment or cure was available. The CDC also states there are no vaccines to prevent AGS.

Which ticks cause alpha-gal syndrome?

In the United States, the lone star tick is most often associated with AGS. A few cases have been reported following bites from blacklegged and western blacklegged ticks, and in other countries other tick species have been linked to AGS.

The lone star tick, Amblyomma americanum, is widely distributed in the Northeast, South, and Midwest United States. The CDC calls it "a very aggressive tick that bites humans." The adult female is distinguished by a white dot, the "lone star," on her back, and nymphs and adult females most frequently bite humans and spread disease.

Its range tracks deer. White-tailed deer are a keystone host, and after lone star tick distribution receded alongside shrinking forest and deer populations, conservation measures and deer relocation since the 1940s have let the tick repopulate its historical range across the eastern United States.

The CDC is careful on one point: not every person bitten by these ticks will develop AGS, and the reason certain people do and others do not is not known. Most reported cases are in adults, but people of all ages can develop AGS.

Why does the reaction take hours to show up?

Symptoms usually appear 2 to 6 hours after eating red meat or dairy, and MMWR puts onset at typically 2 hours or more after exposure.

A second delay sits on top of the first. According to the CDC, it can take weeks to months to have AGS symptoms after a tick bite, so the bite that started the allergy can be weeks or months in the past by the time the first reaction arrives.

A father in a CDC video on delayed AGS symptoms and his struggle to get diagnosed put it this way: "I remember waking up in the middle of the night and feeling really weird... lightheaded, like I was going to fall over, and eventually I was covered in hives."

What do alpha-gal reactions look like?

Reactions differ from person to person, ranging from mild to severe, and some may be life-threatening. People with AGS might not react to every product containing alpha-gal, and some experience different symptoms each time they are exposed, even to the same product. The CDC lists these possible AGS reactions:

  • Hives or itchy rash
  • Nausea or vomiting
  • Severe stomach pain
  • Heartburn or indigestion
  • Diarrhea
  • Cough, shortness of breath, or difficulty breathing
  • Drop in blood pressure
  • Swelling of the lips, throat, tongue, or eye lids
  • Dizziness or faintness
  • A combination of symptoms referred to as anaphylaxis

The CDC instructs anyone having a severe allergic reaction or anaphylaxis to seek immediate emergency care. Anaphylaxis is a potentially life-threatening allergic reaction involving multiple organ systems.

How is alpha-gal syndrome diagnosed?

AGS is diagnosed through a detailed patient history, a physical examination, and a blood test looking for immunoglobulin-E antibodies specific to alpha-gal, known as alpha-gal sIgE. Allergy skin testing for reactions to allergens like pork or beef may also be used.

Here is the catch: a positive alpha-gal sIgE test does not mean a person has AGS. Positive results occur in people who do not have AGS, particularly in regions with lone star ticks. The CDC tells providers to weigh results alongside symptoms, whether the reactions are delayed, and history of tick bites or outdoor exposure. Ordered by providers who know AGS and have a high index of suspicion, MMWR reports the test shows 98% sensitivity and 92% specificity.

Provider familiarity is thin. A web-based survey of 1,500 U.S. health care providers found 42% had never heard of AGS and another 35% were "not too confident" about diagnosing or managing it. Only 5% felt "very confident." Among the 865 who were aware of AGS, 48% did not know the correct diagnostic tests to order.

AGS is not a nationally notifiable condition, though your state may require reporting. The Council of State and Territorial Epidemiologists approved a standardized case definition in 2021, which the CDC notes is for surveillance purposes only and does not replace a clinical diagnosis.

How many people have alpha-gal syndrome?

More than 110,000 suspected AGS cases were identified between 2010 and 2022. Because cases are not nationally notifiable, the CDC says the actual number is not known, but as many as 450,000 people may be affected.

The underlying study drew on the lab responsible for nearly all U.S. testing before 2022. Between January 1, 2017 and December 31, 2022, 357,119 tests covering 295,400 people were submitted from U.S. residences, and 90,018 of those people (30.5%) tested positive. Annual positives rose from 13,371 in 2017 to 18,885 in 2021.

The highest prevalences of suspected cases ran through a nearly contiguous region of the southern, midwestern, and mid-Atlantic United States, particularly parts of Oklahoma, Kansas, Arkansas, Missouri, Mississippi, Tennessee, Kentucky, Illinois, Indiana, North Carolina, Virginia, Maryland, and Delaware. The highest case counts were in Suffolk County, New York (3,746) and Bedford County, Virginia (1,511).

A 2026 MMWR serosurvey tested 3,000 blood donor samples collected between November 2024 and April 2025 across 10 states. Estimated alpha-gal IgE seroprevalence ranged from 1.1% in Washington to 31.2% in Arkansas, with a combined 24.0% across the five highest states: Arkansas, Kentucky, Missouri, Tennessee, and Virginia. The authors are blunt about the limit of that number. Only a small minority of people who are IgE seropositive actually have AGS, so providers should test only patients with clinically compatible symptoms.

How is alpha-gal syndrome managed?

AGS should be managed under the care of an allergist or other healthcare provider, primarily through an avoidance diet. Most providers recommend that patients stop eating meat from mammals such as beef, pork, lamb, venison, or rabbit. Some patients need to eliminate other sources of alpha-gal, including dairy and certain medications.

Beyond meat, the CDC flags gelatin made from beef or pork, products made or cooked with mammal fat such as lard, tallow, or suet, and meat broth, bouillon, stock, and gravy. Some medications and vaccines may contain alpha-gal-containing additives, stabilizers, or coatings, though not all patients react to them. Label reading only goes so far, because cow's milk is the only alpha-gal containing ingredient classified as a major food allergen under federal labeling rules. Foods that do not contain alpha-gal include poultry, fish and seafood, eggs, and fruits and vegetables.

A provider may prescribe an epinephrine auto-injector or nasal spray, and the CDC is explicit that people who use them should still seek emergency care.

Preventing future tick bites is part of the treatment plan, because new tick bites may reactivate allergic reactions to alpha-gal. The CDC also notes that some people who avoid additional bites may be able to tolerate alpha-gal containing products again, which it calls an individualized medical decision.

What the CDC recommends for preventing tick bites

The CDC states that the best way to protect yourself and your family from developing AGS is to prevent tick bites:

  • Use EPA-registered insect repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. Look for an EPA registration number (EPA Reg. No.) on the label, which means the company provided EPA with technical information on the effectiveness of the product.
  • Treat clothing and gear with products containing 0.5% permethrin, which remains protective through several washings. Pre-treated clothing can also be purchased.
  • Shower soon after being outdoors. Showering within two hours of coming indoors has been shown to reduce the risk of getting Lyme disease and may be effective in reducing the risk of other tickborne diseases.
  • Do a full body tick check after returning from potentially tick-infested areas, including your own backyard.

The CDC flags hunters as being at heightened risk, since they spend more time walking through thick grass and densely wooded areas and being low to the ground.

If you think you may have alpha-gal syndrome, talk to your healthcare provider. Nothing here is a diagnosis or a substitute for one.

About Longsleeve

Longsleeve is an EPA-registered picaridin lotion (EPA Reg. No. 101457-1). It repels mosquitoes and ticks for up to 14 hours. It is fragrance-free, with nine disclosed ingredients.

Common questions

Can alpha-gal syndrome go away?

Possibly, for some people. The CDC says some people with AGS who avoid additional tick bites may be able to tolerate alpha-gal containing products again, and calls this an individualized medical decision to make with a provider. As of the CDC's 2023 MMWR report, no treatment or cure was available.

How long after a tick bite do symptoms start?

Two separate clocks. The CDC says it can take weeks to months to have AGS symptoms after a tick bite. Once the allergy exists, individual reactions usually appear 2 to 6 hours after eating red meat or dairy products.

Does a positive alpha-gal blood test mean I have AGS?

No. The CDC states plainly that a positive alpha-gal sIgE test does not mean a person has AGS, and that positive tests occur in people who do not have AGS, particularly in regions with lone star ticks. Diagnosis requires clinically compatible symptoms alongside the antibody result.

Can I still eat chicken, fish, and eggs?

Yes. The CDC's list of foods that do not contain alpha-gal includes poultry such as chicken, turkey, duck, or quail; fish and seafood such as shrimp; eggs; and fruits and vegetables.

Sources

  1. CDC, About Alpha-gal Syndrome. https://www.cdc.gov/alpha-gal-syndrome/about/index.html
  2. CDC, Symptoms of Alpha-gal Syndrome. https://www.cdc.gov/alpha-gal-syndrome/signs-symptoms/index.html
  3. CDC, Managing Alpha-gal Syndrome. https://www.cdc.gov/alpha-gal-syndrome/managing/index.html
  4. CDC, Clinical Diagnosis and Testing (Alpha-gal Syndrome). https://www.cdc.gov/alpha-gal-syndrome/hcp/diagnosis-testing/index.html
  5. CDC, Fast Facts: Products That May Contain Alpha-gal. https://www.cdc.gov/alpha-gal-syndrome/data-research/products-containing-alpha-gal/index.html
  6. Thompson JM, Carpenter A, Kersh GJ, et al. Geographic Distribution of Suspected Alpha-gal Syndrome Cases, United States, January 2017 to December 2022. MMWR Morb Mortal Wkly Rep 2023;72(30):815-820. https://www.cdc.gov/mmwr/volumes/72/wr/mm7230a2.htm
  7. Carpenter A, Drexler NA, McCormick DW, et al. Health Care Provider Knowledge Regarding Alpha-gal Syndrome, United States, March to May 2022. MMWR Morb Mortal Wkly Rep 2023;72(30):809-814. https://www.cdc.gov/mmwr/volumes/72/wr/mm7230a1.htm
  8. Saunders EF, Taylor ML, Jones ES, et al. Alpha-gal Immunoglobulin E Seroprevalence Among Blood Donors, 10 States, 2024 to 2025. MMWR Morb Mortal Wkly Rep 2026;75(25):315-321. https://www.cdc.gov/mmwr/volumes/75/wr/mm7525a1.htm
  9. CDC, Lone Star Tick Surveillance. https://www.cdc.gov/ticks/data-research/facts-stats/lone-star-tick-surveillance.html
  10. CDC, Preventing Tick Bites. https://www.cdc.gov/ticks/prevention/index.html

Last reviewed 2026-08-05 · every claim on this page is sourced above