Although researchers found a link between attractiveness and estrogen levels in women, no relationship was found in women wearing cosmetics. Make-up may mask cues normally seen in the face, they believe.

The new findings could explain the underlying reason why men prefer women with feminine faces. It is the first study to demonstrate that a woman's facial appearance is linked to her underlying health, because estrogen is the hormone that affects reproductive health and fertility.

These effects on appearance are likely to depend on the action of estrogen throughout puberty.

Make-up Masks the Effect

Psychologist Miriam Law Smith and colleagues of the University of St. Andrews photographed the faces of 59 women between 18 and 25 years of age and analyzed their sex hormone levels.

Women with higher levels of estrogen were rated as more attractive, healthy and feminine looking than those with lower levels.

Interestingly, no relationship between appearance and estrogen was found in women wearing make-up. Researchers believe that while make-up improves facial appearance, it may be masking cues normally seen in the face.

Fertility Advertisement

"Women are effectively advertising their general fertility with their faces," says Law Smith.

"Our findings could explain why men universally seem to prefer feminine women's faces. In evolutionary terms, it makes sense for men to favor feminine, fertile women," she adds. "Those that did would have had more babies."