In the animal kingdom, some primates produce reddened faces in order to show off and attract mates. Humans apparently do the same, to some extent.
In a study published this week in the journal PLoS ONE, researchers at the University of St. Andrews in Scotland measured how skin color varies according to the amount of oxygen in the blood. Oxygenated blood is a bright red color, and deoxygenated blood has a slightly bluish-red color. Then they presented computerized graphics of young people's faces to study participants and allowed them to change the color of the faces to make them look as healthy as possible.
For all the faces, participants added more oxygen-rich blood color to improve a healthy appearance. A healthy appearance, the researchers note, has been shown to be a major characteristic of sexual attraction.
Skin contains tiny blood vessels that carry oxygenated blood to skin cells. The process nourishes skin cells and allows the body to release heat during exercise. People who are physically fit or have higher levels of sex hormones have more of these blood vessels and flush more easily than people who are unhealthy, unfit, elderly or who smoke, researchers said.