Alpha-gal syndrome (mammalian meat allergy)
Alpha-gal syndrome is an IgE-mediated allergy to the carbohydrate galactose-alpha-1,3-galactose, acquired after tick bites, causing characteristically delayed reactions 3 to 6 hours after eating mammalian (red) meat. The delayed timing makes it easy to miss; diagnosis uses alpha-gal specific IgE, and management is avoidance of mammalian meat and derived products with epinephrine for reactions.
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What this article covers
- Overview
Definition: alpha-gal syndrome is an IgE-mediated allergy to the carbohydrate galactose-alpha-1,3-galactose (alpha-gal), found in non-primate mammalian tissue.
- Epidemiology
Geographic clustering: occurs where the implicated ticks are endemic.
- Risk factors
Tick bites: the key sensitizing exposure (lone star tick and others).
- Pathophysiology
Tick-bite sensitization: tick salivary components induce IgE against alpha-gal.
- Clinical features
Delayed reactions: urticaria, angioedema, and anaphylaxis 3 to 6 hours after mammalian meat, often at night after an evening meal.
- Differential diagnosis
Idiopathic anaphylaxis: recurrent anaphylaxis where alpha-gal is the unrecognized cause, distinguished by a positive alpha-gal IgE that is absent in truly idiopathic disease (Anaphylaxis).
- Diagnosis
Establish with alpha-gal specific IgE in the right clinical context: the diagnostic basis is a history of delayed (3-to-6-hour) reactions after mammalian meat, often with prior tick bites, confirmed…
- Management
First, treat reactions as anaphylaxis: Epinephrine 0.3 to 0.5 mg IM into the anterolateral thigh, repeated every 5 to 15 minutes as needed.
- Complications
Recurrent nocturnal anaphylaxis: from unrecognized delayed reactions.
- Prognosis
Good with avoidance: eliminating mammalian meat prevents reactions.
- Prevention
Avoid mammalian meat and, as needed, derived products (dairy, gelatin) based on individual sensitivity.
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Related articles
- Anaphylaxis
Anaphylaxis is an acute, potentially fatal systemic hypersensitivity reaction from massive mast cell and basophil mediator release, presenting within minutes as skin, respiratory, cardiovascular, and gastrointestinal involvement after allergen exposure. It is a clinical, treat-first diagnosis, and intramuscular epinephrine is the immediate life-saving therapy.
- Urticaria
Urticaria is transient, pruritic, edematous wheals from mast cell histamine release, classified by duration into acute (under 6 weeks) and chronic (6 weeks or longer, usually spontaneous/idiopathic). Diagnosis is clinical with minimal testing, and treatment is stepwise second-generation H1 antihistamines up-titrated as needed, adding omalizumab for refractory chronic disease.
- Angioedema
Angioedema is self-limited, non-pitting swelling of the deep dermis and submucosa that follows one of two mechanisms: mast cell (histamine) mediated, which occurs with urticaria and responds to epinephrine and antihistamines, or bradykinin mediated, which occurs without urticaria and does not. Distinguishing the two determines whether treatment is allergic therapy or bradykinin-targeted therapy, and airway involvement is the central danger.