ABSTRACT
Solar radiation, or sunlight, which is a combination of ultraviolet rays (UV), visible rays, and infrared rays, is responsible for the life on earth and also determines its climate. Photobiology deals with the study of detrimental and useful interactions of non-ionizing radiation in living organisms. The UV and visible radiations are a constant part of the human environment and play important roles in health, disease, and therapy. Photomedicine is one of the most inspiring and interdisciplinary fields in medicine that involves the research and application of photobiology with respect to health and diseases. With aging, the skin of an individual undergoes morphological and physiological changes caused by intrinsic and extrinsic factors that contribute to cellular aging and consequent skin aging. Clinically it was observed that due to sun radiation, human skin becomes thicker, more flaccid, and more pigmented; there is also an early appearance of skin wrinkles and other skin changes, such as skin cancer. These days, there are numerous treatments for aging skin, and one of the best of them is with the use of phototherapy, which uses laser diodes and light-emitting diodes (LEDs). In the present chapter, basic aspects of photobiology and the light/tissue interaction process will be examined, together with the importance of treatment parameters. The phototherapy principles and their role in the fast-developing indication of skin rejuvenation are explored.
