An allergic reaction to meat-based meals had researchers stumped — until they connected the condition to bites from certain ticks.
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.
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:
Symptoms of alpha-gal syndrome may include:
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.
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:
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.
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:
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:
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:
Health care providers can diagnose alpha-gal syndrome based on your personal history and certain medical tests.
Your health care provider will likely ask you:
Your provider also might give you a physical exam.
Other tests used to diagnose alpha-gal syndrome may include:
Alpha-gal syndrome treatment involves avoiding the foods that cause your reaction. Always check the ingredient labels on store-bought foods. Make sure they don't have red meat or meat-based ingredients, such as:
Check soup stock cubes, gravy packages and flavor ingredients in prepackaged products. Ask your health care provider or allergist for a list of foods to avoid, including meat extracts used in flavoring. The names of some meat-based ingredients make them easy to miss.
Be extra careful when you eat at restaurants and social get-togethers. Many people don't understand how serious an allergic food reaction can be. And few people know that meat allergies exist. Even a small amount of red meat can cause a serious reaction.
If you're worried that a food may contain something you're allergic to, don't try it. Do what you can to lower your risk. For example, you could bring your own food to a party if guests are making food on a shared cooking surface.
For a serious allergic reaction, you may need a shot of epinephrine and emergency care. Many people with allergies carry a device called an epinephrine auto-injector. It's a syringe and concealed needle that injects a single dose of medication when you press it against your thigh. If you've been diagnosed with alpha-gal syndrome, your doctor or allergist likely will prescribe an epinephrine auto-injector.
Symptoms of alpha-gal syndrome may lessen or even disappear over time. This is especially true if you don't get any more bites from ticks that carry alpha-gal. Some people with this condition can eat mammal food products again after 1 to 2 years if they don't get any more tick bites.
To get the most from your appointment, it's a good idea to be well prepared. Here are some tips to help you talk with your health care provider.
Some basic questions to ask your provider include:
Your health care provider will probably ask you questions, such as:
If you think you have alpha-gal syndrome, avoid eating red meat until your appointment. If you have a serious reaction, get emergency help.