With professional electrolysis, an effect on tattoos is very unlikely.
Electrolysis goes below your ink, to the base of the hair follicle. It destroys the growth cells in that one follicle, making it a very precise art. With laser hair reduction, the treatment can act unpredictably when presented with tattoos. When considering laser hair removal, the location of your tattoos in relation to the treatment area is very important. Laser is attracted to pigment in both your unwanted hair and your tattoo ink. Even if the laser technician isn't working directly over the tattoo, the nearby pigment can attract the heat. Good laser technicians will keep at least an inch away from the tattoo, working around it. They may also use a shield to reflect the laser energy away from your ink. Regardless, the tattooed area will require a different method of permanent hair removal. Electrolysis is the only permanent hair removal method recommended for tattoos.
-Beth