May 18, 2023 | Black & Kletz Allergy
Mammalian meat allergy which is also known as alpha-gal syndrome causes an immediate hypersensitivity reaction hours after eating beef, pork, lamb, venison, or any other mammalian meat product. Although the allergy was first described in patients with hives (i.e., urticaria) and severe life-threatening reactions such as anaphylaxis, there is now a new phenotype of mammalian meat allergy that has different presenting symptoms. The new and increasingly recognized phenotype is called gastrointestinal (GI) alpha-gal. Gastrointestinal alpha-gal presents with GI symptoms such as abdominal pain, diarrhea, nausea, and vomiting without the predominant skin, respiratory, or circulatory symptoms.
Individuals with mammalian meat allergy or alpha-gal syndrome have an allergy to the galactose alpha-1,3-galactose, a sugar molecule on the cells of all non-primate mammals which is not present in humans. Lone star ticks can transfer this molecule to humans, by first feeding the mammals, and subsequently biting the humans. Since the galactose alpha-1,3-galactose molecule is foreign to humans, antibodies are formed in order to fight the foreign sugar molecule. When this occurs, the individual becomes sensitized to the molecule. The antibodies produced are called IgE antibodies that are specific towards the galactose alpha-1,3-galactose sugar molecule.
After the sensitization to the galactose alpha-1,3-galactose sugar molecule occurs, if the individual eats mammalian meat which naturally contains the galactose alpha-1,3-galactose (i.e., alpha-gal antigen), the alpha-gal antigen binds to the IgE antibodies present on the mast cells that richly populate the GI tract. As a result of the binding, these mast cells degranulate and release large quantities of histamine and other chemical mediators into the bloodstream. These chemical mediators in turn can act on sensory nerve endings to cause pain, intestinal smooth muscles to cause contractions, and/or mucous glands to cause the secretion of mucous.
When patients seek care for frequent abdominal pain, bloating, cramping, and/or diarrhea, they are often diagnosed as having irritable bowel syndrome (IBS), if no organic cause for these symptoms is identified. Some of these patients could have been previously sensitized to alpha-gal and their symptoms could be an indicator of an allergic reaction. The onset of symptoms could be several hours after the ingestion of the mammalian meat, as opposed to other common immediate type of hypersensitivity reaction (e.g., egg allergy, peanut allergy, seafood allergy), where symptoms usually begin within minutes of the exposure to the food.
A history of awakening up at night from sleep with gastrointestinal distress may suggest alpha-gal given the typical hours delay that occurs in this condition from alpha-gal ingestion to the subsequent reaction. Patients who have a history of tick bites or enjoy outdoor pursuits are at a higher risk for this allergy.
Diagnosis:
Alpha-gal syndrome or mammalian meat allergy is a clinical diagnosis with supporting laboratory findings (i.e., a positive alpha-gal antibody level in the blood). A diagnosis of alpha-gal syndrome may be made in patients with consistent symptoms and an increased alpha-gal IgE titer whose symptoms resolve or improve after adhering to an alpha-gal–avoidance diet, where mammalian meat is avoided.
The clinical presentation of this syndrome can be highly variable and unpredictable. Many patients who have been are previously sensitized, may not have symptoms every time they consume mammalian meat. At other times however, they can have a severe reaction after consuming even a small quantity of mammalian meat.
It should be noted that the gold standard for diagnosing food allergies typically is by an oral food challenge. In individuals with mammalian meat allergy however, there is usually at least a couple or more hours-long delay time until the allergic reaction occurs. Since the allergic reaction is delayed and may also be inconsistent, an oral food challenge is not reliable and thus not used to diagnose mammalian meat allergy.
Management:
The cornerstone of managing alpha-gal syndrome is to eliminate alpha-gal from the diet. Individuals diagnosed with this condition should not eat pork, beef, lamb, venison, rabbit, whale, or any other mammalian meat. In essence, any animal with hair as well as products made from these mammals (e.g., lard, butter, milk) should be avoided. Dairy does contain smaller amounts of alpha-gal, particularly ice cream, cream, and cream cheese, which have a high fat content.
Gelatin is derived from the collagen in pig or cow bones. As such, foods that contain gelatin (e.g., marshmallows, gummy bears, gelatin candies) also may trigger allergic reactions. In addition, processed foods can have small amounts of animal-derived products. Restaurants may cross-contaminate foods with alpha-gal which may be a problem for patients with high levels of sensitivity to alpha-gal.
Fish, shellfish, turkey, chicken, and other fowl are acceptable for patients with alpha-gal.
Prevention:
Alpha-gal–allergic individuals should take measures to avoid further tick bites because additional tick bites may worsen the allergy. Performing regular tick checks, showering soon after activities in grassy and woody areas, creating a barrier at the ankles by pulling up tight mesh socks over the pant cuffs on hikes, and treating clothes and boots with permethrin may all help reduce the likelihood of tick bites.
Certain medications such as cetuximab (i.e., Erbitux) and pancreatic enzymes are derived from pigs and may cause problems in mammalian meat-allergic individuals. A company in Blacksburg, VA developed alpha-gal-free pork, which is FDA-approved but not yet widely available. Another option for alpha-gal allergic individuals is to consume plant-based alternatives to meat commonly found in companies like Beyond Meat or Impossible (e.g., Impossible burger).
All patients diagnosed with alpha-gal allergy should carry a self-injectable epinephrine device (e.g., EpiPen, Auvi-Q, Adrenaclick) for use in case of a systemic reaction following an inadvertent exposure to mammalian meat. If a self-injectable epinephrine device is used, the patient should go immediately to the closest emergency room.
The board certified allergists at Black & Kletz Allergy have been diagnosing and treating food allergies and intolerances as well as mammalian meat allergy (i.e., alpha-gal) for many years. If you or your child suffers from food allergies, food intolerances, eosinophilic esophagitis, hives (i.e., urticaria), swelling episodes (i.e., angioedema) please call us to make an appointment. Alternatively, you can click Request an Appointment and we will respond within 24 hours by the next business day. Black & Kletz Allergy has offices in Washington, DC, McLean, VA (Tysons Corner, VA), and Manassas with on-site parking all 3 locations. Our Washington, DC and McLean, VA locations are Metro accessible and we offer a free shuttle between our McLean, VA office and the Spring Hill metro station on the silver line. We look forward to helping you with all your allergy, asthma, and immunology needs as we have been doing in the Washington, DC, Northern Virginia, and Maryland metropolitan area for more than a half century.
