Anosmia after exposure to a pyrethrin-based insecticide: a case report.

We present the case of a subject developing anosmia, preceded by nasal transient irritation and short lasting phantosmia and torqosmia, upon re-entrance into a room treated with a pyrethrin-based insecticide. The concentration of the insecticide in the room is unknown, but relatively high levels are predicted basing upon the modality of exposure and by the irritation symptoms in the subject. Despite corticosteroids therapy, anosmia has persisted unmodified for more than three years; according to, and based on evidence in the literature on olfactory disturbance prognosis, anosmia in this patient is likely to be permanent. The significance of this case report is related to the current wide use of insecticides containing pyrethrin and pyrethroids and highlights the need for more adequate attention to lowering airborne concentrations of pyrethrins and pyrethroids prior to re-entering the treated rooms. In particular, in a closed space sprayed with pyrethrins and pyrethroids insecticide, any irritant symptoms and/or dysosmia should be immediately considered relevant warning signs, and must be avoided.