Red meat allergy is a relatively new allergy that allergists have been seeing increasingly over the last several years. The most common food allergies that allergy doctors usually see are wheat, milk, soy, eggs, peanuts, nuts, shellfish and fish. But red meat allergy is being seen in increasing amounts. The reaction was found out to originate from the lone star tick, Amblyomma americanum. To develop this red meat allergy, this lone star tick bites someone and it stimulates allergy (IgE) production to a protein called alpha-gal. When red meat is later ingested by a sensitized individual who got bit by the lone star tick (there is alpha-gal in the red meat), the allergy IgE antibodies then bind to it and cause a release of mediators such as histamine.
The reaction consists of anaphylaxis, hives and swelling in response to mammalian meat, such as beef, lamb, pork or venison and even some dairy products. Alpha-gal antigen can also be found in medications such as Cetuximab which is used to treat colorectal cancer. Pharmaceutical manufacturers do not currently test products for alpa-gal content. Alpha-gal has also been found in meat byproducts such as gelatin (Jell-O, marshmallows or capsules) and magnesium stearate, which would lead to allergy reactions as well after taking medications containing these ingredients. Currently there is no comprehensive list of medications that contain meat byproducts. Alpha-gal is not found in avian, reptile or fish sources.
Red meat allergy, also known as the alpha-gal allergy can be tested in the lab by getting alpha-gal IgE levels in the blood. Although red meat allergy is not a common food allergen, with a history of tick bites and reactions after eating red meat, one must always be concerned about possible alpha-gal allergy. Red meat allergy can present also with a delayed reaction, sometimes even several hours after ingestion of red meat.
If you have reactions after eating red meat and have a history of tick bites, you should see an allergist or an allergy doctor to see if you have red meat allergy by being sensitized to alpha-gal.
Update June 22, 2024
A recent study looked into the intrinsic risk factors for alpha-gal syndrome. Age or sex did not seem to contribute to it. Type A or O blood, childhood allergies, food allergies or a family history of alpha-gal syndrome were more likely to develop it. Patients were also likely to report long healing times for insect bites or stings.
The burden of alpha gal syndrome is increasing with approximately 15,000 new cases a year. Approximately half a million people currently have it in the USA now.