Biological Effects of Laser Light Lasers can strengthen damaged cells. Using photochemical processes, laser light inserts bio-photons into damaged cells. The cells begin to produce energy (ATP), which improves their function, assists their division, strengthens the body’s immune system and causes the secretion of various hormones. The tissues are healed, and pain disappears. If damaged cells have died, the bio-photons help the division of neighboring cells, generating new tissues, and bring about healing.

Lasers commonly in use for laser therapy (LT) operate at a wavelength between 600 and 1060 nanometers (nm). Laser devices in this range are known to be safe because they do not include wavelengths in the lower end of the spectrum, which includes X-RAYs and Gamma Rays that cause destructive ionization in the cell. The first lasers used for LT were gas-tube, helium neon lasers at 632nm. Developed in the 1960's, these lasers were very expensive to purchase and too difficult to operate, limiting their availability to just a few well-financed researchers.

In the 1980s however, technological advances allowed for the emergence of relatively inexpensive laser diodes with a wide range of wavelengths. Many Therapeutic Lasers were developed and sold during this period, but were all very low power, around 1 miliwatt (mW). The development of devices for LT has proceeded in such small steps because rather than being driven by the demand for LT devices, the production and availability of laser diodes is driven by the massive demand for laser diodes in technology such as compact disc players, laser scanners, and for a wide range of defense applications. As these technologies matured in the 1990's, they were able to handle much higher power outputs, as high as 500mW, resulting in shorter treatment times for LT applications.