Acute laryngeal obstruction presumed secondary to thiomersal (merthiolate) delayed hypersensitivity.

A patient treated his slight score-throat with a thiomersal first aid spray. The next day, because of continued discomfort, he repeated its use. Laryngeal obstruction followed within hours. Emergency tracheostomy produced prompt improvement. Patch testing revealed an extreme spreading reaction to thiomersal. It is our interpretation that the acute laryngeal obstruction was delayed hypersensitivity to this first aid spray.