I'm not sure but I think high powered blue laser light might be linked to cancer .  I used to have a 1w one and it came with some warnings.  Fun though.,(reply>), Laser light is concentrated light; no magic there. (Okay, the 'in-phase' part has some effects, but not on skin.)<br>   While blue light <i>does</i> have some ionization potential, the dead layer of skin really does shield from that. Ultraviolet is the real danger.