Allergy

Alpha Gal Reaction

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Alpha Gal Reaction, Alpha-Gal Reaction, Alpha-Gal Allergy, Alpha-Gal Syndrome, Red Meat Allergy

  • See Also
  1. Tick Borne Illness
  2. Food Hypersensitivity
  • Epidemiology
  1. Prevalence U.S.: 450,000 estimated cases in U.S.
  2. Lone Star Tick is active in eastern, southeastern and south central U.S. states
  • Mechanism
  1. Occurs after Lone Star Tick Bite (Amblyomma Americanum), found in the eastern and southeastern United States
  2. Sensitization and Antibody formation to Galactose-alpha-1,3-galactose (alpha-gal) due to IgE cross reactivity
  3. Alpha-gal are Carbohydrates present in both tick Saliva and red meat (lamb, pork, beef, venison, rabbit)
  4. In contrast, alpha-gal is not present in the Muscle of primates including humans (hence the potential for sensitization)
  5. Syndrome was first described in 2007 by Dr. Thomas Platts-Mills
  • Findings
  1. New sudden, Allergic Reaction (Urticaria, Anaphylaxis) to red meat (beef, lamb, pork, venison, rabbit)
    1. Initial reaction is a delayed, IgE mediated Allergic Reaction
    2. Symptom onset 2-6 hours after ingestion after red meat (or derived product) ingestion
  2. Common symptoms
    1. Gastrointestinal (Abdominal Pain, Nausea or Vomiting, Diarrhea)
    2. Urticaria (or other pruritic rash)
  3. Severe reactions
    1. Angioedema (facial swelling)
    2. Dyspnea
    3. Anaphylaxis
  • Associated Conditions
  • Other Lone Star Tick related illnesses
  1. Tularemia
  2. Ehrlichiosis
  3. Heartland Virus
  4. Bourbon Virus
  5. Southern Tick Associated Rash Illness (STARI)
  • Differential Diagnosis
  • Red Meat Allergy
  1. Alpha-Gal Syndrome (described on this page)
  2. Primary Beef Allergy
    1. Young children with Atopic Dermatitis (esp. with Cow's Milk Allergy)
  3. Pork-Cat Syndrome
    1. Patients with cat allergy develop pork allergy (and in some cases beef allergy)
    2. Primarily seen in teens and young adults
  • Labs
  1. Alpha-Gal IgE
    1. Consider testing in idiopathic gastrointestinal symptoms after red meat ingestion
  • Management
  1. See Allergic Reaction
  2. See Anaphylaxis
  3. Allergist referral for severe reactions
  4. Reaction Treatment
    1. Epinephrine Home Injectable Devices (e.g. Epi-Pen)
    2. Antihistamines (e.g. Cetirizine, Diphenhydramine)
  5. Prevent exposure
    1. Avoid all red meat products
    2. Additional measures in more severe reactions (or if symptomatic with these additional exposures)
      1. Avoid animal derived products (e.g. cow's milk, gelatin)
      2. Medications, Vaccines or supplements that are mammal derived (e.g. lactose, lanolin)
  • Course
  1. Alpha-Gal antibodies wane over-time (without re-exposure from Lone Star Tick Bite)
    1. Patients may once again tolerate some red meat products with time
  • Prevention
  1. See Prevention of Vector-borne Infection
  • Resources
  • Patients
  1. Alpha-Gal (Mayo Clinic)
    1. https://www.mayoclinic.org/diseases-conditions/alpha-gal-syndrome/symptoms-causes/syc-20428608
  2. Alpha-Gal (CDC)
    1. https://www.cdc.gov/ticks/alpha-gal/index.html
  • References
  1. (2025) Presc Lett 32(7): 40-1
  2. Commins (2011) J Allergy Clin Immunol 127(5): 1286-93 [PubMed]
  3. Wilson (2019) Curr Opin Allergy Clin Immunol 19(3):229-35 +PMID: 30844847 [PubMed]