A novel form of anaphylaxis has recently surfaced which was discovered to be an IgE antibody response to galactose-alpha-1, 3-galactose (alpha-gal), which is an antigen found in red meat. IgE is an antibody created by our immune system in response to an allergen, which then leads to the development of an allergic reaction. In this case, patients will develop an allergic response following exposure to alpha-gal, an allergen. Patients with these symptoms often are difficult to diagnose are their symptoms are more delayed and could be different than the typical IgE mediated food hypersensitivity.

What Role do Ticks Play in the Alpha-Gal Allergy?

    Ticks, which have been found to be the culprit behind the development of an alpha-gal allergy, carry alpha-gal molecules from the animals that they bite and transmit these molecules to humans. For reasons that are still unknown, certain individuals develop mild to severe allergic reactions in response to alpha-gal molecules, which are introduced to the body through consumption of red meat, including beef, pork, and lamb. In the U.S., patients will develop symptoms following a Lone Star tick bite, although the species of tick causing the condition does vary by country. While this condition is most prevalent in the southeastern United States, it can also be found in parts of New York, New Jersey, New England, to even Texas and Oklahoma. The prevalence of the condition is dependent on the tick population in the area and, due to the migration of ticks, the condition is now extending to occur in northern and central parts of the United States as well.

Link Between Alpha-Gal Allergy and Cetuximab

    Cetuximab is a drug used to treat head, neck, and colorectal cancer. Cetuximab also contains alpha-gal molecules and has been found to be a culprit in inducing alpha-gal sensitivity. It has been noted, however, that individuals who have been alpha-gal sensitized due to Cetuximab exposure also live in regions with higher Lone Star tick populations. This then suggests a link between the two factors, although the mechanism behind the direct link is still unknown.

Symptoms of Alpha-Gal Allergy

    One of the reasons why alpha-gal allergy is so difficult to diagnose is due to the delayed onset of symptoms. Individuals with an increased sensitivity to alpha-gal will suffer from delayed anaphylaxis following consumption of red meat, unlike most food allergies which lead to immediate allergic reactions. Symptoms of reactions can range anywhere from a runny nose to itchiness, rash, hives, swelling of the lips, tongue, or throat, difficulty breathing, abdominal pain, diarrhea, nausea, vomiting, or anaphylaxis. Researchers believe the reaction is so delayed due to the prolonged amount of time required to digest alpha-gal molecules before they enter the circulatory system, at which point the reaction occurs. These symptoms can then occur anywhere from 3-6 hours following consumption of red meat, making it difficult for physicians to immediately identify a link between the consumption of red meat and the patient’s reaction. Not to mention, use of a variety of products with animal sources may contain alpha-gal in sufficient quantities which may result in a reaction. Some of these products can include porcine heart valves, bovine cartilage, and some gelatin products depending on the production process.

How is Alpha-Gal Allergy Diagnosed/Treated?

    In any individual with suspected alpha-gal allergy, a detailed history will always be taken to ensure that alpha-gal is indeed the cause. Further blood testing can be ordered, if indicated, which analyzes the level of IgE anti-alpha-gal antibodies in the blood. A high level suggests a sensitivity to alpha-gal. Skin testing can also be performed for foods such as beef, pork, lamb, and dairy. As skin testing is sensitive, a negative result indicates there is a 95% chance that the individual is not allergic to the allergen. A positive result, on the other hand, has the potential to be a false positive and should, therefore,  be considered along with the patient’s clinical history in order to determine its relevance.

    The treatment plan for individuals with alpha-gal allergy is strict avoidance of red meat, such as beef, pork, or lamb. While most individuals with alpha-gal allergy can tolerate dairy, they should still monitor for symptoms following consumption. If accidental exposure does occur, they should always have injectable epinephrine on hand ready to use in case of an anaphylactic reaction. If any anaphylactic reaction does occur, 911 should be contacted immediately after the injection of epinephrine. Individuals with this allergy should always exercise caution when eating out and read food labels prior to purchasing food. Symptoms of alpha-gal have been reported to disappear over time in certain individuals if they continue to avoid exposure to Lone Star ticks. As always, patients should exercise caution and consult with their allergist prior to trying red meat, even if they suspect that symptoms have disappeared.

    Alpha-gal allergy, while rare, is a difficult condition to live with. Many support groups exist for individuals with this condition which may aid in the comfort levels of recently diagnosed individuals trying to determine their new diet regimen and lifestyle. Research is still currently underway as there continue to be aspects of alpha-gal allergy which have yet to be understood. For more information on alpha-gal allergy, please see the links below: