In thermolysis, a hotter treatment at shallow depth is due to which factor?

• A. Hair diameter
• B. Current density
• C. Skin moisture
• D. Surface area

Answer: (B)

The main idea is how heat is produced and where it concentrates during thermolysis. Heat comes from the tissue’s resistance to the current, so the rate of heat generation depends on current density—the amount of current per unit area at the tissue–electrode interface. A higher current density means more energy deposited in a small, superficial region, making the treatment hotter near the surface. As the current spreads into deeper tissues, it covers a larger area, so the current density—and thus heating—decreases with depth. Hair diameter, skin moisture, and surface area can influence overall impedance and energy needs, but they don’t determine the depth at which heat concentrates as directly as current density does.