There may be a biological reason why women use blush — it’s advertising.
A new study from England found that a woman’s facial color may change during her menstrual cycle, with redness increasing during ovulation.
These changes may signal to men that a woman is ovulating (the time when conception is most likely). However, this facial redness is too subtle to be detected by the human eye.
"Women don't advertise ovulation, but they do seem to leak information about it, as studies have shown they are seen as more attractive by men when ovulating," said lead study author Hannah M. Rowland, PhD, of the University of Cambridge, in a press release.
From the standpoint of species survival in humans, a long-term investment from the male is better for the female and her offspring. This is because, unlike many other species, human children have a long developmental period.
In some animal species that advertise ovulation, intercourse only occurs during a female's fertile period. However, in humans, sexual activity may happen when a woman is not ovulating.
According to Dr. Rowland and team, primates — including humans — are attracted to red. This may be why some women subconsciously change their naturally occurring facial redness during ovulation by using makeup like blush or by wearing red clothing.
To look at the possibility of facial reddening to signal ovulation, Dr. Rowland and team photographed 22 women without makeup every day for at least one month. The photographs were taken with a special camera that picks up on tiny changes in color.
Dr. Rowland and team also tested and tracked hormonal changes in these women.
Skin redness was found to peak during ovulation and remain high during the last part of the menstrual cycle. These changes were not detectable to the human eye, however.
"We had thought facial skin color might be an outward signal for ovulation, as it is in other primates, but this study shows facial redness is not what men are picking up on — although it could be a small piece of a much larger puzzle," Dr. Rowland said.
This study was published in the July issue of the journal PLOS One.
Study author Dr. Robert Burris disclosed support from an Anniversary Research Fellowship at Northumbria University. Study authors Drs. Martin Stevens and Jolyn Troscianko disclosed support from the Biological Sciences Research Council. Dr. Rowland disclosed support from an Institute Research Fellowship at the Institute of Zoology.