This updated Medicines Q&A addresses the signs and symptoms of local anaesthetic hypersensitivity, differential diagnoses and management of a patient with suspected allergy to local anaesthetics used in dentistry.
- Allergy to amide local anaesthetics is rare. Allergic reactions are most likely to occur with ester local anaesthetic agents; these are not used routinely in dentistry.
- Adverse effects experienced after administration of local anaesthetics may be mistaken for allergic reactions, but often there is another explanation for the symptoms.
- True allergic reactions to local anaesthetics are either immediate hypersensitivity reactions (type I – angioedema, urticaria, pruritus, chest tightness, wheezing, fall in blood pressure) or delayed hypersensitivity reactions (type IV – localised reaction at the injection site, contact dermatitis).
- Due to the rarity of local anaesthetic allergy, if a patient experiences signs and symptoms suggestive of an allergic response, consideration should be given to other possible causes of the symptoms e.g. toxicity (sedation, light headedness, slurred speech, mood alteration, diplopia, disorientation and muscle twitching) or a psychogenic reaction (anxiety, skin flushing, blotchy red rash, bronchospasm, sweating, tachycardia, syncope, hyperventilation, nausea and vomiting).
- Where local anaesthetic allergy is strongly suspected, patients should be referred for allergy testing for confirmation.