A device that uses light to send hair follicles to sleep, making skin smooth for weeks at a time, without shaving or waxing, is being patented by Philips.

Laser light can be used to kill hair follicles by making them so hot that they literally explode. But such destructive "photoepilation" is painful and can also cause skin irritation.

Researchers at Philips’ Lab in Eindhoven, in the Netherlands, have found that short, weak pulses of near infrared light causes follicles to change from their natural growing state to a dormant state, known as the "telogen phase".

The Philips device uses light from a halogen lamp. Pulses lasting 15 milliseconds each are filtered so that only 600-950 nanometre wavelengths reach the follicles below. Moving the device slowly over the skin spreads about 15 joules of light energy onto each square centimetre.

A sensor can also be used to automatically adjust treatment intensity to suit different skin and hair types. Three treatment sessions, over the course of two weeks, reduces hair growth by 90%, Philips claims.

Read the full razor light patent application.