[Biostimulation with low-intensity lasers--physics or metaphysics?]

The use of low-intensity lasers for biostimulation continues to produce controversies. This paper presents the basic principles of light propagation in tissue. Tissue properties such as fluorescence, absorption and scattering initiate a gradual loss of any "laser-specific" property of the light with distance from the irradiated surface. One of the aims of the discussion is to indicate if a given biological response is expected to be specifically dependent on a laser source, or if the same result also ought to be expected from more conventional light sources.