http://blink.ucsd.edu/safety/research-l ... fects.html
Laser effects on the skin
Thermal (burn) injury is the most common cause of laser induced skin damage. Thermal damage is generally associated with lasers operating at exposure times greater than 10 microseconds and in the wavelength region from the near ultraviolet to the far infrared.
The principal thermal effects of laser exposure depend on:
◦The absorption and scattering coefficients of the tissues at the laser wavelength
◦Irradiance or radiant exposure of the laser beam
◦Duration of the exposure and pulse repetition characteristics, where applicable
◦Extent of the local vascular flow
◦Size of the area irradiated
Tissue damage may also be caused by thermally induced acoustic waves following exposures to sub-microsecond laser exposures. Repetitively pulsed or scanning lasers involve a thermal process wherein the effects of the pulses are additive.