Alpha Gal Syndrome and Red Meat Allergy

Alpha-gal syndrome (AGS) is a red meat allergy linked to tick bites, specially bites from the lone star tick. This tick can carry alpha-gal (galactose-α-1,3-galactose)—a sugar molecule found in the cells of many mammals we eat—that leads to allergic reactions in humans.

People bitten by ticks will alpha-gal can build up an immune response to the molecule, causing them to experience mild to severe allergic reactions to red meat and other meat from mammals. While not as common, some people can also react to alpha-gal found in cow's milk products and gelatin.

What Causes a Red Meat Allergy? 

People aren't born with an allergy to alpha-gal. You can develop an alpha-gal allergy if alpha-gal enters your bloodstream via an infected tick bite, which triggers your immune system to react to alpha-gal as a defense mechanism. These antibodies your body makes will remain in your system, and the next time you consume red meat that also contains alpha-gal, your body may combat it.

The most common cause of alpha-gal syndrome is linked to lone star tick bites, which are active 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. But 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.

While not as common, other ticks that can cause alpha-gal syndrome include:

• Blacklegged ticks (U.S.)
• Cayenne ticks (Central American)
• Asian longhorn ticks (Asia)
  

Researchers are still determining why alpha-gal causes different levels of allergic reactions in different people, or why some people don't develop alpha-gal syndrome despite being exposed. However, studies have theorized that people may be more likely to develop alpha-gal syndrome if they have more than one tick bite.

Symptoms of Red Meat Allergy

Alpha-gal symptoms can range from mild to life-threatening allergic reactions after eating red meat and animal products containing alpha-gal. Symptoms vary 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 2-6 hours after eating red meat or other products that may contain alpha-gal. Research shows people often have allergic reactions at night, around 10 p.m.

Symptoms of alpha-gal syndrome can include:

• Hives or itchy skin rash
• Nausea or vomiting
• Severe stomach pain
• Diarrhea
• Indigestion or heartburn
• Coughing or wheezing
• Swollen lips, tongue, throat, or eyelids
• Shortness of breath and difficulty breathing or swallowing
• Heart palpitations
• Feeling faint or dizzy
• Low blood pressure
• Heart palpitations
  

Severe allergic reactions to alpha-gal can lead to anaphylaxis (aka 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.

How Red Meat Allergy is Diagnosed

An allergist typically diagnoses alpha-gal syndrome with an allergy blood test. During this test, a healthcare provider draws a blood sample from your arm and sends the sample to a lab. The blood is analyzed for high levels of alpha-gal immunoglobulin-E (IgE) antibodies—proteins your immune system creates to protect your body from allergic reactions. People considered positive for alpha-gal syndrome typically have alpha-gal IgE levels greater than 0.1 IU/mL.

Your 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. These tests involve dropping allergens on areas of the skin and then pricking the skin to see if the area develops a red bump after 15 to 20 minutes (a sign of an allergy). However, skin prick tests are unreliable in detecting beef, pork, or lamb allergies. They are not a standard method to test for alpha-gal syndrome.

Available Treatments

Treating alpha-gal syndrome involves managing allergic reactions and avoiding foods with alpha-gal. For example, avoiding red meat can help people prevent allergic reactions to alpha-gal and potentially lower antibody levels that cause the allergy.

Most people with alpha-gal syndrome will need to restructure their diets to avoid the following meats:

• Beef
• Venison
• Lamb
• Goat
• Rabbit
• Buffalo
• Pork  
  

While not as common, some people may need to avoid other foods and products that come from mammals with alpha-gal, these include:

• Cow's milk products
• Lard, tallow, or suet
• Bovine collagen
• Pork or beef gelatin (including gelatin-coated medications)
• Red meat broth and gravy
• Lanolin
• Vaccines containing gelatin, glycerin, magnesium stearate, or bovine extract

If an allergic reaction does occur, your healthcare provider may suggest the following allergy treatments:

• Long-acting oral antihistamine: Daily medications that help relieve allergy symptoms for 8-12 hours, including Allegra (fexofenadine) or Xyzal (levocetirizine).
• Short-acting oral antihistamines: Medications taken when symptoms start for quick relief up to 4-6 hours, including Unisom and Benadryl (diphenhydramine).
• Oral cromolyn solution: Medication taken before meals to help treat gastrointestinal symptoms like diarrhea, vomiting, and upset stomach, including Gastrocrom (cromolyn).
• Epinephrine injection: An adrenaline shot that helps treat anaphylactic shock by relaxing airway muscles and tightening blood vessels, including EpiPen and Auvi-Q (both brand names of epinephrine injection).
  

How To Prevent Red Meat Allergy

Preventing and avoiding tick bites is the best way to prevent alpha-gal syndrome. Some ways you can reduce your risk of tick bites include:

• Avoid areas of tall grass where ticks like to hide
• Treat clothing and outdoor gear with permethrin (an insecticide)
• Wearing pre-treated permethrin clothes while hiking or camping  
• Check for ticks on your body and clothes after being outdoors 
• Remove embedded ticks with fine-tipped tweezers (grabbing the tick close to the skin)
• Check your pets for ticks
• Mow your yard frequently and pick up leaves
  

A Quick Review

Alpha-gal syndrome is a red meat allergy caused by tick bites. People with alpha-gal syndrome develop antibodies that fight alpha-gal. As a result, 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.

The lone star tick in the southeastern U.S. is the most common cause of alpha-gal syndrome, but some cases are also inked to blacklegged ticks.

If you suspect you have alpha-gal syndrome, talk to your healthcare provider. They can test your blood for antibodies and help you devise a plan to avoid alpha-gal products and manage allergic reactions.