What is a meat allergy?
Meat allergy or alpha-gal syndrome is a specific type of allergic reaction that has only recently been identified. In the majority of documented cases in the US, the allergy begins after a bite from a Lone Star tick, which transmits a sugar molecule in the blood called alpha-gal.
In some people, this leads to a severe reaction from the immune system which then causes allergy to red meat.
Most cases of meat allergy occur in the southeastern part of the US, as this is the main habitat of the Lone Star tick. The alpha-gal syndrome has also been spread in Europe, Asia and Australia where other kinds of tick carry the alpha-gal molecule.
Lone Star Ticks (Amblyomma americanum) Credit: Melinda Fawver / Shutterstock
What is a tick bite?
Ticks are a type of arthropod parasite (same family as spiders) that bites painlessly and often goes unnoticed attached to its host because the ticks are tiny and their bites are painless. They are carriers of many diseases that go under-detected due to the nature of the bite.
The molecule that causes meat allergy is contained in the saliva of the tick that gets into contact with its host. The molecule is called alpha-gal. A tick acquires this molecule from biting and ingesting blood sheep or cows. The carbohydrate alpha-gal epitope is also present in animal proteins including those in red meat.
A clinical observation conducted in the regions of Sydney and New South Wales demonstrated an association between tick bite reactions and red meat allergy. All participants in the study reported experiencing allergic reactions after consuming red meat. Beef most commonly triggered a reaction, followed by lamb and pork. All of the participants lived in regions that have been endemically infested with several tick species. In all but one case, tick exposure was associated with development of red meat allergy in one to six months.
As compared to any other type of an allergic reaction, the allergic reaction to meat is delayed in time, with the signs and symptoms typically develop within three to six hours of contact with meat. Due to this fact, it is a challenge to connect the symptoms with eating meat.
The symptoms can affect the skin, the respiratory tract, gastrointestinal tract and the cardiovascular system. There are several classic allergy symptoms associated with meat allergy:
- Itchy skin
- Swelling of lips, tongue
- Shortness of breath
- Abdominal pain, diarrhea, vomiting or nausea
- Anaphylaxis: This is a severe and potentially deadly reaction which restricts breathing
Triggers of the allergic reaction
When the body of sensitized persons encounters meat containing alpha-gal, the body considers it as a threat. In response to the first encounter, the body produces specific immunoglobulin E (IgE) antibodies that attach to immune cells throughout the body.
Every time a person with meat allergy eats meat, the allergen attaches to the IgE antibodies to release histamine and other chemicals that function is to protect the body from this assumed threat. The symptoms can vary from mild to severe depending on the tissue in which the antibodies are released.
Managing severe allergic reactions
The most severe reaction caused by meat allergy is anaphylaxis. The first line of treatment of anaphylaxis is epinephrine. Epinephrine is used instead of antihistamines because it reverses the swelling of the airways and raises low blood pressure. It is used to quickly reverse the most dangerous components of this life-threatening reaction. It is common for the symptoms of a severe allergic reaction to reoccur, thus having two doses of epinephrine is recommended.
Epinephrine must be taken immediately in the case of severe symptoms such as shortness of breath. Repetitive coughing, difficulty swallowing, tightness in the throat, abdominal pain or a combination of these should also be taken seriously and medical help should be sought immediately.
Repeated doses of epinephrine may be needed. Side effects of epinephrine usage such as dizziness, anxiety and restlessness may be experienced acutely.
Mayo Clinic Minute: Rise in tick-related meat allergy
Diagnosis and Treatment
There are two main types of tests used to diagnose meat allergy and any other allergy. The first type is a blood test. The blood tests confirms and measures the amount of alpha-gal antibodies in your bloodstream. This is the key diagnostic method for the alpha-gal syndrome. The second type of test that can be conducted by a physician is a skin test. The test involves pricking the skin and exposing it to a small number of substances extracted from red meat. Doctors can also test the skin reaction to individual types of red meat.
It is advisable to avoid areas where ticks live, especially wooded areas with long grass. The risk of developing alpha-gal syndrome can be decreased if simple measures are taken. If going to a grassy place it is advisable to wear long clothes that cover your whole body. In addition to that, the use of repellants is recommended.
Like any other allergy, red meat allergy should be diagnosed and treated appropriately to avoid severe allergic reactions which in some cases can be deadly. There are many species of ticks in the US, and tick bites can transmit several diseases to humans.
Persons living in areas where ticks are endemic should check their bodies daily to ensure that no ticks are attached to the skin. Ticks should be removed as soon as possible by grasping them with a fine-tipped tweezers at the point where the tick is attached to the skin and pulling firmly upward. Clean the bite area and hands after removal.