A new study has revealed that the regions of the face that redden during sexual stimulation also slightly heat up during innocent social interactions.
For the study, Amanda Hahn and colleagues at St Andrew's University in Fife, UK, used a heat-sensitive camera to map small changes of temperature in the faces of young heterosexual women while an experimenter touched them with an instrument they were told was measuring skin colour.
Touching the palm or elbow had no effect, but contact with the cheek or top of the breastbone raised the temperature around the eyes, mouth and nose by 0.2-to 0.5 degrees centigrade on average, and by a full degree in certain spots.
An earlier study had found this area heats up in sexually aroused men.
The female subjects reported few or no feelings of arousal or embarrassment, but their facial temperature rose more when the experimenter was a young man.
"What is surprising is the magnitude," New Scientists quoted Hahn as saying.