Elderly armpits can lift your spirits

Hormones detected by human smell can alter your mood

The armpit smells of old ladies are the latest mood-enhancing substances to be uncovered by scientists - but they warn that those of young men may have the reverse effect.

The Pennsylvania-based team believe that the effect may be due to the human ability to detect the presence or absence of hormones in sweat which signal aggression, reports "New Scientist" magazine.

Denise Chen, at the Monell Chemical Senses Center in Philadelphia recruited 30 volunteers in six different age categories - young girls and boys, young adult men and women, and men and women in their 70s.

Perfume and deodorant ban

The volunteers were banned from using perfumes or deodorants, or eating strong smelling food for four days, although they were allowed to take showers using unscented soap.

Throughout this period, a gauze pad strapped under the arm absorbed any odour they produced.

Then more than 300 university students sampled smells taken at random, filling in before and after questionnaires designed to test their mood.

People who had inhaled the samples taken from the armpits of old ladies responded significantly more positively.

Ms Chen said: "Old women had an uplifting effect".

But results showed the smell of young men had a noticeably "depressive effect", an outcome which might have been anticipated by any parent of a teenage boy.

In between these extremes, the smell of older people generally improved mood, as did the smell of females.

Hormonal signal

Jeannette Haviland, who also worked on the research, suggested that hormones in the body odour of the young might act as a signal of aggression.

She pointed to a recent study which showed that people can distinguish between the odours of both happy and frightened people.

Hormonal changes in old age, she said, were likely to make the odour of the elderly, particularly women, signal approachability.