Category: Clinical Engineering. A hyfrecator is a low power medical electro-surgical diathermy. (Diathermy: from the Greek ~ Dia - through and thermy- heat) The hyfrecator is used to rapidly and selectively destroy tissue by the passage of an electric current through the tip of the hyfrecator as it touches the skin. This will burn off the tissue in question. Small skin lesions can be treated without anaesthesia but the procedure may require topical or local anaesthesia.