A strobe light is created by discharging electricity very quickly like the flash of a camera. The circuitry can be used so that a powerful electronic pulse goes through a coil of copper wire. It is the centre of this coil that is held against the suspect blemish on the skin.
I got the idea from Dr. Bob Beck on Blood Electrification for cleansing, parasite zapping, neutralisation of HIV, etc.
I am a hobbyist and professional electrical engineer. Because of my engineering background I was sceptical about the claims of zappers. When these spots disappeared my whole family were amazed.