A dose-dependent delayed hypersensitivity reaction to acetaminophen after repeated acetaminophen intoxications.

We report a case of a 29-year-old woman with a borderline personality disorder who presented with intentional substantial acetaminophen (paracetamol) overdosage on nine occasions during a period of 21 months. In most cases, the patient presented at the hospital within 4 h after ingestion and was treated with gastric lavage, activated charcoal, laxatives and intravenous N-acetylcysteine. During the sixth overdosage the patient developed a rash on her chest and shoulders which was considered an anaphylactoid reaction to N-acetylcysteine. Therefore she was treated with oral methionine subsequently, but developed the rash again. The rash was then ascribed to the repeated high-doses of acetaminophen and treatment with N-acetylcysteine was reinstituted. This case shows that when an anaphylactoid reaction occurs after an acetaminophen overdose and treatment with N-acetylcysteine, acetaminophen must also be taken into account as the cause of the anaphylactoid reaction before effective therapy with N-acetylcysteine is withheld.