Pheromones are chemical signals that help animals to communicate. Members of the same species respond to each other’s pheromone releases by changing a behaviour or undergoing a physiological change.
For example male house mice pheromones trigger aggression in other males and speed up puberty in young female mice. Though pheromones have been discovered across the animal kingdom, so far evidence for a human pheromone is elusive.
‘Smelly t-shirt’ experiments, where participants sniff the armpits of worn t-shirts, are sometimes mistakenly thought of as pheromones. These, however, are smells that help identify how compatible our immune systems are with one another. Importantly pheromones aren’t unique to individuals in this way but are common to all members of a species.