Alpha-gal syndrome is a recently identified type of food allergy to red meat and other products made from mammals. In the United States, the condition is most often caused by a Lone Star tick bite. The bite transmits a sugar molecule called alpha-gal into the person's body. In some people, this triggers an immune system reaction that later produces mild to severe allergic reactions to red meat, such as beef, pork or lamb, or other mammal products.

The Lone Star tick is found predominantly in the southeastern United States, and most cases of alpha-gal syndrome occur in this region. The tick can also be found in the eastern and south central United States. The condition appears to be spreading farther north and west, however, as deer carry the Lone Star tick to new parts of the United States. Alpha-gal syndrome also has been diagnosed in Europe, Australia and Asia, where other types of ticks carry alpha-gal molecules.

Researchers now believe that some people who have frequent, unexplained anaphylactic reactions — and who test negative for other food allergies — may be affected by alpha-gal syndrome. There's no treatment other than avoiding red meat and other products made from mammals.

Avoiding tick bites is the key to prevention. Protect against tick bites by wearing long pants and long-sleeved shirts and using insect repellents when you're in wooded, grassy areas. Do a thorough, full-body tick check after spending time outside.

Signs and symptoms of an alpha-gal allergic reaction are often delayed compared with other food allergies. Most reactions to common food allergens — peanuts or shellfish, for example — happen within minutes of exposure. In alpha-gal syndrome, reactions usually appear about three to six hours after exposure. Red meat, such as beef, pork or lamb; organ meats; and products made from mammals, such as gelatins or dairy products, can cause a reaction.

Signs and symptoms of alpha-gal syndrome may include:

• Hives, itching, or itchy, scaly skin (eczema)
• Swelling of the lips, face, tongue and throat, or other body parts
• Wheezing or shortness of breath
• A runny nose
• Stomach pain, diarrhea, nausea or vomiting
• Sneezing
• Headaches
• A severe, potentially deadly allergic reaction that restricts breathing(anaphylaxis)

Doctors think the time delay between eating red meat and developing an allergic reaction is one reason the condition was overlooked until recently. A possible connection between a T-bone steak with dinner and hives at midnight was far from obvious.

When to see a doctor

See your primary care doctor or a doctor who specializes in the diagnosis and treatment of allergies (allergist) if you experience food allergy symptoms after eating — even several hours after eating. Don't rule out red meat as a possible cause of your reaction, especially if you live or spend time outdoors in the southeastern United States or in other parts of the world where alpha-gal syndrome is known to occur.

Seek emergency medical treatment if you develop signs or symptoms of anaphylaxis, such as:

• Difficulty breathing
• Rapid, weak pulse
• Dizziness or lightheadedness
• Drooling and inability to swallow
• Full-body redness and warmth (flushing)

A Lone Star tick bite most commonly causes the condition in the U.S. Bites from other types of ticks can lead to the condition in the U.S., Europe, Australia and Asia.

Tick bites

Ticks that cause alpha-gal syndrome are believed to carry alpha-gal molecules from the blood of the animals they commonly bite, such as cows and sheep. When a carrier tick bites a human, the tick injects alpha-gal into the person's body.

For unknown reasons, some people have such a strong immune response to these molecules that they can no longer eat red meat or products made from mammals without a mild to severe allergic reaction. People who are exposed to many tick bites over time may develop more-severe symptoms.

The cancer drug cetuximab

People with antibodies related to alpha-gal syndrome can have allergic reactions to the cancer drug cetuximab (Erbitux). Cetuximab-induced cases of this condition are most common in regions with a high population of Lone Star ticks, suggesting a possible link between Lone Star tick bites and an increased vulnerability to alpha-gal syndrome. More research is needed to understand the connection between ticks that carry alpha-gal in certain regions and cases of alpha-gal syndrome that don't seem directly linked to tick bites.

Researchers think the hallmark time-delayed reaction of alpha-gal syndrome is due to the alpha-gal molecules taking longer than other allergens to be digested and enter your circulatory system.

Doctors don't yet know why some people develop alpha-gal syndrome after exposure and others don't. The condition mostly occurs in the southeastern United States and parts of New York, New Jersey and New England. You're at increased risk if you live or spend time in these regions and:

• Spend a lot of time outdoors
• Have received multiple Lone Star tick bites
• Have a mast cell abnormality such as indolent systemic mastocytosis

In the past 20 to 30 years, the Lone Star tick has been found in large numbers as far north as Maine and as far west as central Texas and Oklahoma in the United States.

Alpha-gal syndrome can also occur in other parts of the world such as Europe, Australia and parts of Asia, where bites from certain types of ticks also appear to increase your risk of the condition.

Alpha-gal syndrome can cause food-induced anaphylaxis, a medical emergency that requires treatment with an epinephrine (adrenaline) injector (EpiPen, Auvi-Q, others) and a visit to the emergency room.

Anaphylaxis signs and symptoms can include:

• Constriction of airways
• Swelling of the throat that makes it difficult to breathe
• A severe drop in blood pressure (shock)
• Rapid pulse
• Dizziness, lightheadedness or loss of consciousness

Based on recent research, doctors now believe that some people with unexplained, frequent anaphylaxis may be living with undiagnosed alpha-gal syndrome.

The best way to prevent alpha-gal syndrome is to avoid areas where ticks live, especially wooded, bushy areas with long grass. You can decrease your risk of getting alpha-gal syndrome with some simple precautions:

• Cover up. When in wooded or grassy areas, wear shoes, long pants tucked into your socks, a long-sleeved shirt, a hat and gloves. Try to stick to trails and avoid walking through low bushes and long grass. Keep your dog on a leash.
• Use insect repellents. Apply insect repellent with a 20% or higher concentration of DEET to your skin. Parents should apply repellent to their children, avoiding their hands, eyes and mouths. Keep in mind that chemical repellents can be toxic, so follow directions carefully. Apply products with 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 especially vigilant after spending time in wooded or grassy areas.
• It's helpful to shower as soon as you come indoors. Ticks often remain on your skin for hours before attaching themselves. Showering and using a washcloth might remove unattached ticks.
• Remove a tick as soon as possible with tweezers. Gently grasp the tick near its head or mouth. Don't squeeze or crush the tick, but pull carefully and steadily. Once you've removed the entire tick, dispose of it and apply antiseptic to the bite area.

Doctors can diagnose alpha-gal syndrome using a combination of your personal history and certain medical tests.

Your doctor will likely start by asking about your exposure to ticks, your signs and symptoms, and how long it took for symptoms to develop after you ate red meat or other mammal products. He or she might also perform a physical exam.

Additional tests used in the evaluation of alpha-gal syndrome may include:

• Blood test. A blood test can confirm and measure the amount of alpha-gal antibodies in your bloodstream. This is the key test for diagnosis of alpha-gal syndrome.
• Skin test. Doctors prick your skin and expose it to small amounts of substances extracted from commercial or fresh red meat. If you're allergic, you develop a raised bump (hive) at the test site on your skin. Your doctor or allergist may also test your skin for an allergic reaction to individual types of red meat because there are different kinds of allergies to meat.

As with any food allergy, alpha-gal syndrome treatment involves avoiding the foods that cause your reaction. Always check the ingredient labels on store-bought foods to make sure they don't contain red meat or meat-based ingredients, such as beef, pork, lamb, organ meats or gelatins. Check soup stock cubes, gravy packages and flavor ingredients in prepackaged products. Ask your doctor or allergist for a list of foods to avoid, including meat extracts used in flavoring. The names of some ingredients make them difficult to recognize as meat based.

Use extra caution when you eat at restaurants and social gatherings. Many people don't understand the seriousness of an allergic food reaction, and few realize meat allergies even exist. Even a small amount of red meat can cause a severe reaction.

If you are at all worried that a food may contain something you're allergic to, don't try it. Come prepared to social events to avoid risk of exposure. For example, if you're attending a party where guests prepare food on a shared cooking surface, bring your own precooked food.

For a severe allergic reaction, you may need an emergency injection of epinephrine and a visit to the emergency room. Many people with allergies carry an epinephrine autoinjector (EpiPen, Auvi-Q, others). This device is a syringe and concealed needle that injects a single dose of medication when pressed against the thigh. Once you've been diagnosed with alpha-gal syndrome, your doctor or allergist likely will prescribe an epinephrine autoinjector.

Symptoms of alpha-gal syndrome may lessen or even disappear over time if you don't get any more bites from ticks that carry alpha-gal. Some people with this condition have been able to eat red meat and other mammal products again after one to two years without additional bites.

To get the most from your appointment, it's a good idea to be well prepared. Here's some information to help you get ready for your appointment and to know what to expect from your doctor.

• Description of your symptoms. Be ready to tell your doctor what happened after you ate red meat, including how long it took for a reaction to occur. Be prepared to describe the type of red meat you ate as well as the portion size.
• History of tick bites or possible exposure to ticks. Your doctor will need to know where you've spent time outdoors and how often, as well as how many tick bites you're aware of having experienced.
• Make a list of all medications you're taking. Include vitamins or supplements.
• Take a family member or friend along, if possible. Sometimes it can be difficult to recall all the information provided to you during an appointment. Someone who comes with you may remember something you missed or forgot.
• Write down any questions you have.

Some basic questions to ask your doctor include:

• Are my symptoms likely caused by a red meat allergy?
• What else might be causing my symptoms?
• What tests do I need?
• What's the best treatment?
• Should I see a specialist?
• Is there a generic alternative to the medicine you're prescribing?
• Are there brochures or other printed material that I can take with me? What websites do you recommend?
• Do I need to carry an epinephrine autoinjector?

What to expect from your doctor

Your doctor is likely to ask you a number of questions, including:

• When did you begin noticing symptoms?
• What type of meat and how much did you eat before symptoms appeared?
• After eating red meat, how long did it take symptoms to appear?
• Are you currently spending time or have you in the past spent time outdoors in tick-infested areas?
• Have you been bitten by a tick in the past? How many times? What did these ticks look like?
• Did you take any over-the-counter allergy medications, such as antihistamines, and if so, did they help?
• Does your reaction seem to be triggered only by red meat or by other foods as well?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?

What you can do in the meantime

If you suspect you have alpha-gal syndrome, avoid eating red meat until your doctor's appointment. If you have a severe reaction, seek emergency help.