What Is Alpha-Gal Syndrome?
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Medically reviewed by Susan Bard, MD
Alpha-gal syndrome (AGS) is a red meat allergy linked to tick bites, specifically bites from the lone star tick. This tick can carry alpha-gal (galactose-α-1,3-galactose), which is a sugar molecule in the cells of many animal products. Alpha-gal leads to allergic reactions in humans.
People bitten by ticks with alpha-gal can build up an immune response to the molecule, causing them to have mild to severe allergic reactions to red meat and other meat from mammals. Some people can also react to alpha-gal in cow's milk products and gelatin, although it's not as common.
Related: What Is Hypereosinophilic Syndrome?
What Is Alpha-Gal Allergy?
People aren't born with an allergy to alpha-gal. However, you can develop an alpha-gal allergy if the sugar molecule enters your bloodstream via an infected tick bite. The tick bite triggers your immune system to react to alpha-gal as a defense mechanism. The antibodies your body makes will remain in your system. Your body may combat alpha-gal the next time you consume red meat that also contains it.
The most common cause of AGS is linked to lone star tick bites. Lone star ticks are active from April to late August and can be found from Oklahoma to Maine on shaded tall grass or the tips of low-lying branches and twigs. Not everyone bitten by a lone star tick will develop a red meat allergy. Ticks must have alpha-gal in their saliva when they bite you.
Other ticks that can cause AGS, although not as common, include:
Asian longhorn ticks (Asia)
Blacklegged ticks (U.S.)
Cayenne ticks (Central America)
It's unclear why alpha-gal causes different levels of allergic reactions in different people or why some don't develop AGS despite being exposed. Some evidence suggests that people may be more likely to develop AGS if they have more than one tick bite.
Alpha-Gal Allergy Symptoms
Alpha-gal allergy symptoms can range from mild to life-threatening after eating animal products containing alpha-gal. Symptoms vary from person to person, and some people with a red meat allergy don't have consistent allergic reactions. Some people may also be sensitive to food, medications, and self-care products that contain alpha-gal from gelatin and cow's milk.
Red meat allergy symptoms usually occur two to six hours after eating red meat or other animal products that contain alpha-gal. Research has shown that people often have allergic reactions at night, around 10 p.m.
Alpha-gal allergy symptoms include:
Coughing or wheezing
Feeling faint or dizzy
Gastrointestinal symptoms (e.g., abdominal pain, diarrhea, nausea, or vomiting)
Heart palpitations
Hives or itchy skin rash
Indigestion or heartburn
Shortness of breath and difficulty breathing or swallowing
Swollen lips, tongue, throat, or eyelids
Severe allergic reactions to alpha-gal can lead to anaphylaxis (anaphylactic shock). This life-threatening, whole-body allergic reaction can make your blood pressure drop dramatically and narrow your airways so you can't breathe.
Diagnosis
An allergist typically diagnoses AGS with an allergy blood test. They will draw a blood sample from your arm and send it to a lab.
The blood is analyzed for high levels of alpha-gal immunoglobulin-E (IgE) antibodies. The immune system creates these proteins to protect against allergic reactions. People who are positive for AGS have alpha-gal IgE levels greater than 0.1 international units per milliliter (IU/mL).
An allergist will also discuss your medical history and perform a physical exam to identify signs of allergic reactions. They may also perform an allergy skin test to rule out other allergies. This test involves dropping allergens on areas of the skin and then pricking it to see if the area develops a red bump after 15 to 20 minutes. A skin prick test is unreliable in detecting beef, pork, or lamb allergies and is not a standard method to test for AGS.
Treatments
Treating AGS involves managing allergic reactions and avoiding foods with alpha-gal. Avoiding red meat, for example, can help prevent allergic reactions to alpha-gal and lower antibody levels that cause the allergy.
Most people with AGS will need to restructure their diets to avoid the following meats:
Buffalo
Goat
Lamb
Pork
Rabbit
Venison
Some people may need to avoid other foods and products that come from mammals with alpha-gal. These include:
Bovine collagen
Cow's milk products
Lanolin
Lard, tallow, or suet
Pork or beef gelatin (including gelatin-coated medications)
Red meat broth and gravy
Vaccines containing gelatin, glycerin, magnesium stearate, or bovine extract
A healthcare provider may suggest the following allergy treatments if an allergic reaction occurs:
Epinephrine injection: An adrenaline shot that helps treat anaphylactic shock by relaxing airway muscles and tightening blood vessels, including EpiPen and Auvi-Q (epinephrine)
Long-acting oral antihistamine: Daily medications that help relieve allergy symptoms for eight to 12 hours, including Allegra (fexofenadine) or Xyzal (levocetirizine)
Oral cromolyn solution: Medication taken before meals to help treat GI symptoms (e.g., diarrhea, vomiting, and upset stomach), including Gastrocrom (cromolyn)
Short-acting oral antihistamines: Medications taken when symptoms start for quick relief up to four to six hours, including Unisom and Benadryl (diphenhydramine)
The exact reason isn't fully understood, but something in the cancer drug Erbitux (cetuximab) formula can cause allergic reactions in people with AGS. People with a red meat allergy need to avoid medical products like pig and cow heart valves, monoclonal antibodies, heparin, and antivenoms made from animals with alpha-gal.
Prevention
Preventing and avoiding tick bites is the best way to prevent AGS. Some ways you can reduce your risk of tick bites include:
Avoid areas of tall grass where ticks like to hide.
Check for ticks on your body and clothes after being outdoors.
Check your pets for ticks.
Mow your yard frequently and pick up leaves.
Remove embedded ticks with fine-tipped tweezers.
Treat clothing and outdoor gear with permethrin, which is an insecticide.
Wearing pre-treated permethrin clothes while hiking or camping.
Related: What Is a Sun Allergy?
A Quick Review
AGS is a red meat allergy caused by tick bites. People with AGS develop antibodies that fight alpha-gal. People with the allergy have mild to life-threatening allergic reactions to red meat and alpha-gal-containing foods like pork, venison, cow's milk, and gelatin.
Talk to a healthcare provider if you suspect you have AGS. They can test your blood for antibodies and help you devise a plan to avoid alpha-gal products and manage allergic reactions.
FAQs
Frequently Asked Questions
1. Is there a cure for AGS?
There's no cure for AGS. You might manage AGS through dietary changes and allergy management. Limited research has shown that a small percentage of people who achieve negative alpha-gal antibody levels after five years or more could reintroduce red meat without issues.
2. What foods and products should I avoid if I have AGS?
Avoid red meat and other mammalian meats like beef, pork, venison, lamb, goat, rabbit, and buffalo if you have AGS. Some people may need to avoid other products with alpha-gal, like cow's milk, cheese, lard, certain vaccines, and gelatin (including gelatin-coated medications).
3. How long does AGS take to develop?
AGS typically develops within four to six weeks after a tick bite. People with AGS generally have allergy symptoms two to six hours after eating red meat or other animal products that contain alpha-gal.
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