a device for treating the skin , for instance for removing body hair . the device includes a working head , which includes an irradiating device for irradiating the skin surface to be treated , preferably by means of light ; a contact surface surrounding the irradiating device for supporting the working head on the skin surface ; and a safety device for controlling the irradiation and / or for providing a safety signal . the safety device includes a recording device for recording the support of the working head on the skin surface . the contact surface defines a bell - like pressure and / or sound chamber and the recording device encompasses an impermeability sensor device for determining the over - pressure and / or sound impermeability of the pressure and / or sound chamber .