Alpha-gal syndrome is a type of food allergy. It makes people allergic to red meat and other products made from mammals.
In the United States, the condition usually begins with the bite of the Lone Star tick. The bite transfers a sugar molecule called alpha-gal into the body. In some people, this triggers a reaction from the body's defenses, also called the immune system. It causes mild to severe allergic reactions to red meat, such as beef, pork or lamb. It also can cause reactions to other foods that come from mammals, such as dairy products or gelatins.
The Lone Star tick is found mainly in the southeastern United States. Most cases of alpha-gal syndrome are reported in the south, east and central United States. But the condition appears to be spreading farther north and west. Deer are carrying the Lone Star tick to new parts of the country. Other types of ticks carry alpha-gal molecules in different parts of the world. Alpha-gal syndrome has been diagnosed in parts of Europe, Australia, Asia, South Africa, and South and Central America.
Some people may have alpha-gal syndrome and not know it. There are people who often have serious allergic reactions, also called anaphylactic reactions, for no clear reason. Tests also show that they don't have other food allergies. Researchers think that some of these people may be affected by alpha-gal syndrome.
There's no treatment other than avoiding red meat and other products made from mammals. If you have a serious allergic reaction, you may need medicine called epinephrine and treatment at the emergency room.
Avoid tick bites to prevent alpha-gal syndrome. Wear long pants and long-sleeved shirts when you're in wooded, grassy areas. Use bug spray too. Check your whole body for ticks after you spend time outside.
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The symptoms of an alpha-gal allergic reaction usually take longer to start compared with those of other food allergies. Most reactions to common food allergens — peanuts or shellfish, for example — happen within minutes after you are exposed to them. In alpha-gal syndrome, reactions usually appear about 3 to 6 hours after you are exposed. Foods that can cause a reaction include:
- Red meat, such as beef, pork or lamb.
- Organ meats.
- Products made from mammals, such as gelatins or dairy products.
Symptoms of alpha-gal syndrome may include:
- Hives, itching, or itchy, scaly skin.
- Swelling of the lips, face, tongue and throat, or other body parts.
- Wheezing or shortness of breath.
- Stomach pain, diarrhea, upset stomach or vomiting.
The time delay between eating meat products and getting an allergic reaction may be one reason alpha-gal syndrome was not understood at first. For example, a possible connection between a T-bone steak with dinner and hives at midnight is far from clear.
Researchers think they know the reason for the delayed reaction. They say it's due to the alpha-gal molecules taking longer than other allergens to be digested and enter the system that moves blood through the body.
When to see a doctor
Get help if you have food allergy symptoms after you eat, even several hours after you eat. See your primary care health care provider or an allergy specialist, called an allergist.
Don't rule out red meat as a possible cause of your reaction. That's even more important if you live or spend time in parts of the world where alpha-gal syndrome has been reported.
Get emergency medical treatment if you have symptoms of a serious allergic reaction that causes trouble breathing, called anaphylaxis, such as:
- Trouble breathing.
- Rapid, weak pulse.
- Dizzy or lightheaded feeling.
- Drooling and not being able to swallow.
- Full-body redness and warmth, called flushing.
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Most people with alpha-gal syndrome in the U.S. get the condition when a Lone Star tick bites them. Bites from other types of ticks can lead to the condition too. These other ticks cause alpha-gal syndrome in parts of Europe, Australia, Asia, South Africa, and South and Central America.
Experts think the ticks that cause alpha-gal syndrome carry alpha-gal molecules. These come from the blood of the animals they usually bite, such as cows and sheep. When a tick that carries these molecules bites a human, the tick sends alpha-gal into the person's body.
For unknown reasons, some people have a strong immune response to these molecules. The body makes proteins called antibodies. These antibodies target alpha-gal as something the immune system needs to clear out. The response is so strong that people with this allergy can no longer eat red meat. They cannot eat any foods made from mammals without having an allergic reaction. People who get many tick bites over time may develop worse symptoms.
The cancer drug cetuximab
People with antibodies related to alpha-gal syndrome can have allergic reactions to the cancer drug cetuximab (Erbitux).
Research appears to show that cases of this drug allergy are linked to alpha-gal syndrome. The antibodies that the immune system makes to alpha-gal seem to react to the structure of the drug as well.
Health care providers don't yet know why some people get alpha-gal syndrome after exposure and others don't. The condition mostly happens in the south, east and central United States. You're at higher risk if you live or spend time in these regions and:
- Spend a lot of time outdoors.
- Have gotten multiple Lone Star tick bites.
In the past 20 to 30 years, the Lone Star tick has been found in large numbers as far north as Maine. This tick also has been found as far west as central Texas and Oklahoma.
Alpha-gal syndrome also happens in other parts of the world. This includes parts of Europe, Australia, Asia, South Africa, and South and Central America. In those places, bites from certain types of ticks also appear to raise the risk of the condition.
Alpha-gal syndrome can cause a serious allergic reaction called anaphylaxis. It can be deadly without treatment. Anaphylaxis is treated with prescription medicine called epinephrine, also known as adrenaline. You can give yourself a shot of epinephrine with a device called an auto-injector (EpiPen, Auvi-Q, others). You also need to go to the emergency room.
Anaphylaxis symptoms can include:
- Tight, narrow airways.
- Swelling of the throat that makes it hard to breathe.
- A serious drop in blood pressure, called shock.
- Rapid pulse.
- Feeling dizzy or lightheaded, or passing out
Health care providers think that some people who get anaphylaxis often and for no clear reason may be living with alpha-gal syndrome. They just haven't been diagnosed with it.
The best way to prevent alpha-gal syndrome is to avoid areas where ticks live. Be careful in wooded, bushy areas with long grass. You can lower your risk of getting alpha-gal syndrome by following some simple tips:
- Cover up. Dress to protect yourself when you're in wooded or grassy areas. Wear shoes, long pants tucked into your socks, a long-sleeved shirt, a hat and gloves. Also try to stick to trails and avoid walking through low bushes and long grass. If you have a dog, keep it on a leash too.
- Use bug spray. Apply insect repellent with a 20% or higher concentration of the ingredient DEET to your skin. If you're a parent, put the bug spray on your children. Avoid their hands, eyes and mouths. Keep in mind that chemical repellents can be toxic, so follow directions carefully. Apply products with the ingredient permethrin to clothing, or buy pre-treated clothing.
- Do your best to tick-proof your yard. Clear brush and leaves where ticks live. Keep woodpiles in sunny areas.
- Check yourself, your children and your pets for ticks. Be watchful after you spend time in wooded or grassy areas.
- It's helpful to shower as soon as you come indoors. Ticks often stay on your skin for hours before they attach themselves. Shower and use a washcloth to try to remove any ticks.
- Remove a tick with tweezers as soon as possible. Gently grasp the tick near its head or mouth. Don't squeeze or crush the tick. Pull it off with a careful, steady grip. Once you've removed the entire tick, throw it out. Put on an antiseptic where it bit you. That can help prevent an illness.
Mayo Clinic Minute: Ways to avoid ticks
Jeff Olsen: While you're enjoying a hike, ticks are looking for a ride.
Dr. Bobbi Pritt: They get themselves in a position. And they will climb up the nearest object, like this blade of grass here.
Jeff Olsen: It's called questing.
Dr. Bobbi Pritt: It sticks out its legs, and that allows it to grab on to hosts as they walk by.
Jeff Olsen: You can lessen the chances you'll become a host.
Dr. Bobbi Pritt: Using insect repellents is a good idea.
Jeff Olsen: Mayo Clinic parasitic diseases expert Dr. Bobbi Pritt suggests permethrin for your clothing and gear.
Dr. Bobbi Pritt: You can really saturate your gear. Leave them out to dry, and, then, the next day, wear them.
Jeff Olsen: Use permethrin on materials and DEET on skin. Spray the DEET repellent on exposed skin, including your legs and hands. Avoid your face, but be sure to protect your neck. Then, tuck your pants into your socks. And, on your hike, remember to avoid areas where those questing ticks may be perched.
Dr. Bobbi Pritt: That's why you want to stay away from the tall grasses. Stay in the middle.
Jeff Olsen: For the Mayo Clinic News Network, I'm Jeff Olsen.
Nov. 15, 2022