Celery is believed to be an aphrodisiac because it contains androstenone.
is a steroid found in both male and
female sweat and urine. It is also
found in boar's saliva, and in celery
cytoplasm. Androstenone was the first
mammalian pheromone to be identified.
It is found in high concentrations in
the saliva of male pigs, and, when
sniffed by a female pig that is in
heat, results in the female assuming
the mating stance. Androstenone is the
active ingredient in 'Boarmate', a
commercial product made by DuPont sold
to pig farmers to test sows for timing
of artificial insemination.
In humans, androstenone also has been
suggested to be a pheromone; however,
scientific data to support these
claims are scant.
Source: Kirk-Smith, M.D., and Booth, D.A. (1980) "Effect of androstenone on choice of location in others' presence". In H. van der Starre (Ed.), Olfaction and Taste VII, London: Information Retrieval Ltd., pp.397-400.
It is also suggested that we would be unable to sense its presence:
The vomeronasal organ is an auxiliary
olfactory sense organ responsible for
the detection of pheromones as more
than just an odor. Most adult humans
possess something resembling this
organ, but there is no active
function. Humans lack the sensory
cells that exist in other mammals
needed to detect pheromones beyond a
smell. Humans also lack the genetic
ability to produce these sensory cells
Spinney, Laura. "Five things humans no longer need". New Scientist. Retrieved 2008-05-20.