From the Guidelines
Alpha-gal (Alpha-galactose) Allergy
Alpha-gal syndrome is an IgE-mediated allergy that occurs hours after eating beef, pork, other mammalian meat, or mammalian-derived products, causing symptoms such as abdominal pain, diarrhea, nausea, and vomiting without predominant skin, respiratory, or circulatory symptoms 1.
Key Characteristics
- The allergy is to galactose alpha-1,3-galactose, an oligosaccharide on the cells of all nonprimate mammals 1.
- Sensitization to alpha-gal is understood to occur after the bite of a tick or parasitic infection 1.
- The Lone Star tick is strongly implicated in the United States 1.
Clinical Presentation
- Patients with alpha-gal syndrome may experience GI symptoms such as abdominal pain, vomiting, and diarrhea without skin findings or anaphylaxis 1.
- The syndrome can present with nonspecific symptoms like abdominal pain, diarrhea, nausea, or vomiting without predominant skin, respiratory, or circulatory symptoms 1.
Diagnosis and Management
- Alpha-gal syndrome is a clinical diagnosis with supporting laboratory findings, made in patients with consistent symptoms and an increased alpha-gal IgE titer whose symptoms resolve or improve after adherence to an alpha-gal–avoidance diet 1.
- A positive IgE antibody to alpha-gal alone is not enough to establish the diagnosis, particularly in patients with isolated GI distress 1.
- Patients should be directed to adopt an alpha-gal–avoidance diet that eliminates mammalian meat and related products for at least a month, and then re-evaluated to determine whether symptoms have improved or persisted 1.
From the Research
Definition and Characteristics of Alpha-gal Allergy
- Alpha-gal syndrome (AGS) is an allergic response characterized by the formation of specific immunoglobulin E (IgE) antibodies targeting a carbohydrate termed galactose-a-1.3-galactose (a-Gal) 2.
- The symptoms of AGS include rash, nausea, vomiting, and diarrhea, which can occur 3-6 hours after consuming red meat or other mammalian products 3, 4.
- AGS is unique in that the symptoms causing IgE antibodies are directed against a carbohydrate moiety, and the delay between food consumption and the onset of symptoms is unusual compared to other food allergies 5, 6.
Causes and Triggers of Alpha-gal Allergy
- Tick bites, particularly from the Amblyomma americanum species, have been identified as a potential cause of AGS, as the salivary glands and saliva of these ticks contain alpha-gal antigens 2, 4.
- The intake of red meat, medical drugs, vaccines, and antidotes containing a-Gal epitopes can trigger allergic reactions in individuals with AGS 2, 3.
- The oligosaccharide alpha-gal is present in cells and tissues of non-primate mammals, making it a potential allergen for individuals with AGS 5, 6.
Diagnosis and Management of Alpha-gal Allergy
- Diagnosis of AGS can be challenging due to the delayed onset of symptoms and the variability of clinical presentations 3, 4.
- Management of AGS involves avoiding foods and products containing alpha-gal, as well as medications and vaccines that may trigger allergic reactions 3, 6.
- Further research is needed to understand the mechanisms of AGS and to develop effective treatments and management strategies for the disease 5, 6.