'Sex pheromones' don't make you sexy after all

Two of the strongest candidates for human sex pheromones – androstadienone and estratetraenol – have been shown not to make people appear any more attractive in a double-blind trial.

Sex pheromones are chemicals produced by the body that act to attract a mate. Many animals give off pheromones, from moths to goats, but whether or not humans do is still debated.

Androstadienone is a compound made in the human body, and some have claimed that it is a pheromone given off by men that is attractive to heterosexual women. A speed-dating experiment where women were exposed to androstadienone reportedly found the men more attractive, according to one study.

Estratetraenol is a compound made by women and has been proposed to attract heterosexual men. Men watching a video clip of a gender-neutral figure walking were more likely to report that the walks looked feminine if exposed to estratetraenol, another study found.

Put to the test

Both potential pheromones were put to the test in a double-blind trial on 43 heterosexual men and 51 heterosexual women, so that neither experimenters nor study participants knew whether they received pheromone or placebo.

The trial lasted for two days, with each participant exposed to the potential pheromone of the opposite sex on one day and the placebo on the other. On both days the study participants did the same tasks on a computer. They decided whether gender-neutral faces looked more male or female, rating how attractive a range of faces were and judging whether they thought those faces looked like faithful romantic partners or prone to cheating.

The exposure of the women to and of the men to estratetraenol didn't lead to any differences in the participants' performance compared with the placebo, suggesting that neither of the chemicals were working as a sex pheromone.

"If human sex pheromones affect our judgements of gender, attractiveness or unfaithfulness from faces, they are unlikely to be androstadienone or estratetraenol," write the authors, led by Robin Hare of the University of Western Australia, in the paper.

Murky history

These two chemicals were first proposed to be pheromones in 1991, at a conference sponsored by a company with commercial interests in human pheromones, another study on the pheromones notes. Since then scientists have tested various potential effects of the chemicals on human sexual behaviour, with very mixed results.

Some of the claims have bolstered alternative therapy businesses that sell androstadienone and estratetraenol to people hoping to boost their appeal to the opposite sex, for up to £50 for less than 20ml. Patents have even been filed for knickers impregnated with androstadienone or estratetraenol.

"We recommend a return to first principles in the search for human pheromones, and recommend scientific rather than commercial bioassays of human chemical output as an unbiased method of identifying true human pheromones," Hare writes.

The research is published in the journal Royal Society Open Science.