Alpha-gal Syndrome
Alpha-gal Syndrome (AGS): Understanding a Tick-Bite-Associated Allergy
Alpha-gal syndrome (AGS) is a serious, potentially life-threatening allergy that can develop after a tick bite. People with AGS may experience allergic reactions after eating certain foods or being exposed to other products that contain alpha-gal.
In the United States, AGS is most often associated with bites from the lone star tick (Amblyomma americanum), although a few cases have also been reported following bites from blacklegged ticks (Ixodes scapularis) and western blacklegged ticks (Ixodes pacificus).
What Is Alpha-gal?
Alpha-gal, short for galactose-α-1,3-galactose, is a sugar molecule naturally found in most mammals but not in people. Alpha-gal is also found in the saliva of some ticks.
Alpha-gal can be found in:
- Mammalian meat, including beef, pork, lamb, venison, and rabbit
- Milk and other dairy products
- Gelatin made from mammals
- Certain foods or products made with mammalian ingredients
Foods that do not contain alpha-gal include poultry, fish and seafood, eggs, fruits, and vegetables.
What Is Alpha-gal Syndrome?
Alpha-gal syndrome is a serious, potentially life-threatening allergy and a noninfectious tickborne disease.
Certain tick bites can introduce alpha-gal through tick saliva and trigger the production of alpha-gal-specific immunoglobulin E (IgE) antibodies. After this sensitization occurs, exposure to alpha-gal in mammalian meat or other products may cause an allergic reaction.
AGS is sometimes called alpha-gal allergy, red meat allergy, or tick bite meat allergy.
In the United States, the lone star tick is the tick most often associated with AGS. A few cases have also been reported following bites from blacklegged ticks (Ixodes scapularis) and western blacklegged ticks (Ixodes pacificus). Other tick species have been linked to AGS in other countries.
How Common Is Alpha-gal Syndrome?
More than 110,000 suspected cases of AGS were identified in the United States between 2010 and 2022.
However, AGS is not a nationally notifiable condition, so the actual number of cases is unknown. CDC states that as many as 450,000 people in the United States may be affected.
Signs & Symptoms
AGS reactions can vary from person to person and may range from mild to severe or life-threatening.
Possible symptoms include:
- Hives or an 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 eyelids
- Dizziness or faintness
- Anaphylaxis
Unlike many food allergies that cause reactions soon after eating, AGS symptoms usually appear 2–6 hours after exposure to products containing alpha-gal, such as mammalian meat or dairy products. Reactions may also occur after exposure to certain other products containing alpha-gal.
A person with AGS may not react after every exposure, and the type or severity of a reaction can vary from one exposure to another.
It can also take weeks to months after a tick bite for a person to begin experiencing symptoms of AGS.
When to Seek Emergency Care
Seek immediate emergency medical care if you are experiencing a severe allergic reaction or anaphylaxis.
Anaphylaxis is a potentially life-threatening allergic reaction that can affect multiple organ systems.
If your healthcare provider has prescribed an epinephrine auto-injector or epinephrine nasal spray for severe allergic reactions, follow their instructions for its use. People who need to use epinephrine should still seek emergency medical care.
If you think you may have AGS but are not experiencing an emergency, talk with your healthcare provider for evaluation and guidance.
Can a Tick Bite Cause AGS?
Yes. AGS can develop after a tick bite.
In the United States, the lone star tick is most often associated with AGS. A few cases have also been reported following bites from blacklegged and western blacklegged ticks.
Not everyone bitten by these ticks will develop AGS, and researchers are still studying why some people develop the allergy while others do not.
Reducing Your Risk: Tick Prevention
The best way to reduce the risk of developing AGS is to prevent tick bites.
Avoid Tick Habitats When Possible
Ticks are commonly found in grassy, brushy, or wooded areas and in places with high grass and leaf litter.
When hiking or walking in areas where ticks may be present, stay near the center of trails when possible.
Use Tick Repellent
Use an EPA-registered insect repellent containing an approved active ingredient such as:
- DEET
- Picaridin
- IR3535
- Oil of lemon eucalyptus (OLE)
- Para-menthane-diol (PMD)
- 2-undecanone
Always follow the product label and application instructions.
Do not use products containing oil of lemon eucalyptus (OLE) or PMD on children under 3 years old.
Protect Clothing & Gear
Wear long-sleeved shirts and pants when appropriate, and consider using clothing and gear treated with 0.5% permethrin.
Permethrin is intended for treating clothing and gear according to product directions, not for direct application to skin.
Check for Ticks
After spending time outdoors:
- Check your clothing for ticks.
- Examine gear and pets.
- Shower soon after coming indoors.
- Perform a thorough full-body tick check.
- Pay particular attention to areas such as in and around the hair and ears, under the arms, around the waist, between the legs, and behind the knees.
What Should I Do If I Find an Attached Tick?
Remove an attached tick as soon as possible.
CDC recommends using clean, fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible. Pull the tick away from the skin with steady, even pressure. Do not twist or jerk the tick.
After removal, thoroughly clean the bite area and your hands with soap and water, rubbing alcohol, or hand sanitizer.
If fine-tipped tweezers are not available, CDC states that regular tweezers or your fingers may also be used to grasp the tick close to the skin’s surface. Avoid squeezing the tick’s body.
Do not use petroleum jelly, heat, nail polish, or other substances to try to make an attached tick detach.
Keeping clean, fine-tipped tweezers readily available during outdoor activities can help ensure that an attached tick can be removed promptly.
How Is Alpha-gal Syndrome Diagnosed?
If you think you may have AGS, talk with a healthcare provider.
Diagnosis typically involves:
- A detailed medical history
- A physical examination
- A blood test for alpha-gal-specific immunoglobulin E (IgE) antibodies
Allergy skin testing may also be used in some cases.
Importantly, a positive alpha-gal IgE blood test alone does not necessarily mean that a person has AGS. Some people have alpha-gal-specific IgE antibodies without experiencing symptoms.
Healthcare providers consider laboratory results together with compatible symptoms, whether allergic reactions are delayed, and a person’s history of tick bites or outdoor exposure when diagnosing AGS.
What Should I Do If I Have AGS?
AGS should be managed with the help of an allergist or other healthcare provider.
Management may include:
- Identifying and avoiding foods or products that trigger reactions
- Carefully reading food labels
- Preventing additional tick bites
- Learning how to recognize signs of a severe allergic reaction or anaphylaxis
- Following your healthcare provider’s emergency treatment plan
- Talking with your healthcare provider before taking a new medication or receiving a vaccine
Although very rare, some people with severe AGS may react to ingredients in certain medications or vaccines.
New tick bites may reactivate allergic reactions to alpha-gal, so continued tick-bite prevention is particularly important for people with AGS.
What Foods & Products Should People With AGS Avoid?
Not everyone with AGS reacts to the same foods or ingredients. Avoidance recommendations should therefore be individualized with a healthcare provider.
Most healthcare providers recommend that people with AGS avoid mammalian meat, including:
- Beef
- Pork
- Lamb
- Venison
- Rabbit
- Other meats from mammals
Some people with AGS may also react to:
- Gelatin made from beef or pork
- Foods made or cooked with mammalian fat, such as lard, tallow, or suet
- Meat broth, stock, bouillon, or gravy
- Certain dairy products
- Certain medications, vaccines, or other medical products containing mammalian-derived ingredients
Many people with AGS can tolerate milk and dairy products, so dairy does not necessarily need to be eliminated by everyone with AGS. Work with a healthcare provider to determine which foods and products you personally need to avoid.
Some medications and vaccines may contain alpha-gal-containing additives, stabilizers, or coatings, although not everyone with AGS reacts to these ingredients. Animal-derived medical products may also contain alpha-gal.
Although reactions involving certain medications or vaccines are very rare, people with AGS should talk with their healthcare provider before taking a new medication or receiving a vaccine.
Who Can Develop AGS?
People of any age can develop alpha-gal syndrome, although most reported cases have occurred in adults.
Most reported U.S. cases occur in the South, East, and Central United States, areas that substantially overlap with where lone star ticks are commonly found.
Stay Tick Aware
Learning how to prevent tick bites, check for ticks, and properly remove attached ticks can help reduce exposure to ticks and the health concerns associated with them.
Explore our Resources section for additional information about ticks, tick-bite prevention, and proper tick removal.
Medical Disclaimer: This information is provided for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. If you think you may have alpha-gal syndrome, consult a qualified healthcare provider. Seek immediate emergency medical care for a severe allergic reaction or anaphylaxis.
Primary Sources: Centers for Disease Control and Prevention (CDC) — Alpha-gal Syndrome guidance; clinical diagnosis and testing information; products that may contain alpha-gal; AGS management and emergency-care guidance; tick-bite prevention guidance; tick-removal guidance; and CDC’s current AGS research.
Educational Disclaimer
This information is provided for educational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment.
If you develop a fever, rash, unusual fatigue, headache, body aches, nausea, vomiting, or other concerning symptoms following a known or possible tick exposure, contact a qualified healthcare provider and mention the potential tick exposure.
