Halothane hepatitis: toxicity or hypersensitivity?

A 32 year old female developed a severe hepatitis (serum bilirubin 544 mumol/l) one week after a halothane anaesthetic. Six months later a general anaesthetic was administered via a halothane free circuit without incident. A year later a further non halothane anaesthetic was administered this time utilising the routine circuit after briefly flushing the rubber tubing with oxygen. That evening she became febrile and the following day abnormal liver function tests were documented. She remained asymptomatic.