Local anesthetic allergy
True IgE-mediated local anesthetic allergy is rare; most reactions labeled as allergy are vasovagal episodes, systemic toxicity, or effects of added epinephrine. Ester anesthetics are more allergenic than amides, and diagnosis uses skin testing and a graded challenge to identify a safe agent, which is what most evaluations accomplish, and genuine anaphylaxis is treated with intramuscular epinephrine.
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What this article covers
- Overview
Definition: local anesthetic allergy is a hypersensitivity reaction to a local anesthetic, but genuine IgE-mediated allergy is rare.
- Epidemiology
Reactions are common; true allergy is rare: the vast majority of evaluated patients have no IgE-mediated allergy.
- Risk factors
Ester anesthetic exposure: the higher-risk class for true allergy.
- Pathophysiology
True IgE-mediated (rare): specific IgE to the ester (or, rarely, amide) anesthetic or an additive triggers mast cell degranulation.
- Clinical features
True allergic reaction: urticaria, angioedema, bronchospasm, or anaphylaxis shortly after administration.
- Differential diagnosis
Vasovagal syncope: bradycardia and pallor without urticaria or bronchospasm.
- Diagnosis
Establish the true reaction type, then confirm a safe agent with skin testing and a graded challenge: because true IgE allergy is rare, the diagnostic goal is to distinguish genuine allergy from…
- Management
First-line, treat the acute reaction by its true mechanism: for genuine anaphylaxis give epinephrine 0.3 to 0.5 mg IM into the anterolateral thigh, repeated every 5 to 15 minutes, with airway…
- Complications
Anaphylaxis: in the rare true allergic reaction.
- Prognosis
Excellent: evaluation almost always identifies a safe local anesthetic.
- Prevention
Characterize and document the reaction accurately rather than applying a blanket "anesthetic allergy" label.
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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.