It is proposed that LLLT produces a shift in overall cell redox potential in the direction of greater oxidation [45]. Different cells at a range of growth conditions have distinct redox states. Therefore, the effects of LLLT can vary considerably. Cells being initially at a more reduced state (low intracellular pH) have high potential to respond to LLLT, while cells at the optimal redox state respond weakly or do not respond to treatment with light. (http://photobiology.info/Hamblin.html)