Red light therapy appears safe. However, there are some warnings when using therapy.
Eyes
Do not aim laser beams into the eyes, and everyone present should wear appropriate safety glasses.
Tattoo
Treatment over a tattoo with higher irradiance laser may cause pain as the dye absorbs the laser energy and gets hot.
The hair on the head
Treatment of the head and neck with high irradiance laser may cause pain as the melanin in the fine superficial hair follicle absorbs a lot of the laser energy.
Very dark skin
Occasionally some people with very dark skin feel an unpleasant amount of heat.