Idiosyncratic adverse reactions to intramuscular botulinum toxin type A injection.

Three cases of adverse reactions to repeated intramuscular botulinum toxin A (BTA) injections are described: a persistent rash on the face at the site of injection, a localized anaphylactic reaction following BTA injection into one leg, and bilateral ptosis repeatedly following BTA injection into neck muscles. The mechanisms for these idiosyncratic adverse responses are not known.