Androstenone

Androstenone (5a-androst-16-en-3-one) is a steroid found in male sweat.

It is said to have either an unpleasant, sweaty, urinous smell, with varying degrees of unpleasantness depending on the concentration. Around 1/4 of males can not smell androstenone, but noses can learn to smell it.

It has been described as a pheromone and extracts are commercially available as a supposed sex attractant.

Androstenone is normally a signaller of aggression.