Food allergies and sensitivities are a common diagnosis in my office. As an allergy and immunology specialist, I help patients identify allergens that cause a variety of symptoms and reactions, and together we make a plan to prevent future episodes.
Over the past eight years, I have seen a large increase in patients with a mammal meat allergy, caused by tick bites; specifically, this is an allergy to a carbohydrate in (non-primate) mammal meat called alpha-gal. This means that people with this allergy are unable to eat beef, pork, deer meat, etc.
What is alpha-gal?
Alpha-gal is an abbreviation for a carbohydrate molecule called galactose-alpha-1,3-galactose
that is found in most mammals. The molecule is also found in the saliva of the Lone Star tick (and possibly other ticks). People bitten by a Lone Star tick may develop an allergy or sensitivity to the alpha-gal molecule. This means after exposure to the tick, eating mammal meat can trigger the release of histamine in the body and generate symptoms of an allergic reaction.
What are the symptoms of an alpha-gal allergy?
As with other food allergies, signs or symptoms of an allergy to alpha-gal may include:
- Hives and itching
- Swelling of lips, face or eyelids
- Shortness of breath, cough or wheezing
- Abdominal pain, nausea, diarrhea or vomiting
- Anaphylaxis - a severe, potentially life-threatening allergic reaction where blood pressure suddenly drops and airways narrow making it difficult to breathe
- Patients can also have symptoms not common for allergic reactions such as fever and joint pain.
I have found that patients with an alpha-gal allergy almost always have abdominal complaints. Their symptoms include stomach pain, vomiting, and diarrhea starting up to several hours after eating mammal meat. The delay in symptoms is most likely caused by the length of time (usually 3 to 6 hours) for the immune system to recognize the carbohydrate molecule.
(In contract, egg and peanut allergies are caused by a protein, which is recognized much faster by the immune system, explaining why a person with one of those allergies has an almost immediate reaction instead of a delayed reaction.)
How is an alpha-gal allergy diagnosed?
A person experiencing the symptoms listed above should make an appointment with their primary care doctor or an allergy specialist. The provider will review medical history, ask about symptoms, discuss daily routines, etc.
If an alpha-gal allergy is suspected, a blood test will be ordered. This test measures the levels of a specific immunoglobulin E (IgE) antibody. High levels of IgE indicate an allergy or sensitivity to the alpha-gal molecule. The blood test takes several days, up to a week, to come back from the lab. This can frustrate some patients who may have experience with skin tests and their quick results.
But regular skin tests for food allergies identify a protein
in mammal meat. Since alpha-gal is a carbohydrate
, our current tests aren’t effective in finding it through skin testing.
How is it treated?
In one word, avoidance. Treatment of an alpha-gal allergy or sensitivity involves avoiding the food that triggers an allergic reaction. That includes:
- Beef (steak, hamburgers, ground beef)
- Pork (ham, bacon, pork chops, etc.)
- Processed meats (hot dogs, bologna, deli lunch meat)
- Other non-primate mammal meat
In sensitive patients, gelatin can be a problem. Some patients also have trouble with mammal by-products like milk.
Patients with alpha-gal allergy can eat fish, turkey, shell fish and chicken because they are not mammals and do not have alpha-gal.
Additional notes about avoidance:
Does an alpha-gal allergy get better or go away?
- Pay special attention to food labels and ask questions when dining out because meat products appear in places you may not consider. For example, beef stock is often used when making soups and gravies. Restaurants put beef tallow, a traditional cooking fat like lard, in their fryers with French fries and chicken.
- Cooking mammal meat and poultry or fish on the same grill can lead to cross-contamination.
- Additionally, fat content plays an important role in the amount of alpha-gal consumed. Mammal products that have more fat also have more alpha-gal, leading to more severe allergic reactions. A ribeye steak has more fat than a filet, so it has more alpha-gal molecules. Heavy cream or ice cream has more fat than regular milk, so it has more alpha-gal molecules.
- Symptoms such as hives or shortness of breath are treated the same as any other food allergy: in an urgent care or emergency setting with antihistamines, epinephrine and other medications.
Symptoms and reactions to eating mammal meat can improve and eventually go away – unless there are more tick bites. Repeated tick bites greatly increase the risk of continued alpha-gal allergy or sensitivity.
To avoid ticks, wear long-sleeved shirts or pants, use appropriate insect repellants, and check your body for ticks after spending time outdoors. Any observed ticks should be removed carefully by cleaning the site with rubbing alcohol, then using tweezers to pull the tick’s head up carefully from the skin using steady pressure. Do not crush the tick between your fingers and be sure to clean the area and your hands after disposing of the tick.
You can learn more about tick bite prevention, and get tips on removing a ticks that have already bitten the skin, from the CDC.
Some information in this blog is from the AAAAI – American Academy of Allergy, Asthma & Immunology