A natural chemical found in the sweat of men has been shown to act as a primitive love potion that increases their attractiveness in the eyes of women, a study has found.

The substance, which is derived from the male sex hormone testosterone, has a small but significant effect on judgements made by women in a speed-dating situation of a male stranger's attractiveness.

Tamsin Saxton of the University of St Andrews studied the influence of androstadienone by dabbling a drop of it on the upper lip of 50 women who took part in the evening trial before they "dated" a series of men.

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Women of all ages rated the men slightly higher on a scale of attractiveness when given the substance, compared to water or clove oil, but the effect was greatest in younger women aged between 18 and 22, Dr Saxton said.

"For some of the women we gave them androstadienone and we put it in clove oil solution so they just smelt clove oil. Some of the women had clove oil alone, and the third group had just water so there was no odour at all," she told the British Science Festival.

"We got the women to mark how attractive they thought the men were on a one to seven scale after they interacted with each man," she said.

"We found that the women given androstadienone had given slightly higher ratings of attractiveness to the men. That suggested this constituent of sweat does seem to have some kind of impact on attraction," she told the festival.

Little is known about androstadienone other than that it is found in human sweat, both in men and women, and that it is derived from testosterone.

"Some people don't seem to be able to smell it all, some people say it smells OK or a bit sweaty, whereas others say it smells really awful, like babies' nappies," Dr Saxton said.

One hypothesis is that it could be a "pheromone", or chemical messenger that acts between individuals in much the same way that hormones act as messengers within the body. But the idea of human pheromones is highly controversial, she said.

"It's something that people investigate on the topic of pheromones. When you talk of animal pheromones, they are involved in very specific reactions," Dr Saxton said.

"People do value somebody's natural skin smell and it's worth bearing in mind that this may be part of your appeal - how you smell naturally," she told the festival.