How do you know if laser goes through your dermis?

Lasers. Lasers can penetrate the skin directly, (cause a controlled injury) or pass through the skin and target a specific color, (brown for age spot or red for spider veins). If the laser heats the skin it can blister as well. If the laser damages the deep dermis the area will be numb 3rd degree burn, if the skin hurts it is 2nd degree. It is best to ask your laser physician.