Light therapy or phototherapy consists of exposure to specific wavelengths of light using lasers, LEDs, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, for a prescribed amount of time. It has proven effective in treating Acne vulgaris, seasonal affective disorder, and for some people it has ameliorated delayed sleep phase syndrome. It has recently been shown effective in non-seasonal depression. Proponents claim demonstrable benefits for skin conditions such as psoriasis and, more controversially, a degree of "skin rejuvenation."

Ancient medical books are filled with explanations of the importance of getting enough light. For example, the ancient Ayurvedic physician Charaka who lived in the sixth century B.C., recommended sunlight to treat a variety of diseases. For thousands of years people the world over have revered the sun as a great healer; some ancient cultures even worshiped the sun.

In 1980, A.J. Lewy and coworkers published an article in Science that ushered in the modern era of phototherapy. Lewy suggested that secretion of the hormone melatonin could be suppressed by exposing subjects to bright artificial light but not to light of ordinary indoor intensity. It has been shown that melatonin in animals is secreted at night by the pineal gland under the influence of a circadian rhythm. Light rays impinging on the retina are converted into nerve impulses, which influence the secretion of melatonin by connections between the retina and the hypothalamus. This demonstration that one physiologic effect of light in humans, transmitted presumably via the hypothalamus, has a threshold intensity far higher than that required for vision, suggested that there might be other effects of light on the brain that require high-intensity light.

There is no doubt that the sun plays a very important role in our daily lives. During winter, the well-to-do vacations in Caribbean. The summer months are synonymous with spending time in the beach, in spite of all the warning of the potential to get skin cancer. We feel better after spending time in the sun. Today, most of the doctors and medical researchers view the sun more as a healer than a hazard.

We know that lack of sunlight can result in nutritional deficiencies. Without sunlight vitamin D cannot be metabolized in the human body, which can result in rickets. Most enzymes, hormones and vitamins need light for proper functioning. Studies have shown that different lights affect different enzymatic reactions for healing purposes. For example, one of the first test a pediatrician do to a new-born baby is to check for jaundice. If found positive, they are placed under a blue light to cure the disease. So, most of us are given light therapy, without us being aware of it.

Professor Mester of Budapest University conducted experiments to determine the function of light in the cells of animals and humans. He found that the monochromatic light promotes the DNA to use the lipoprotein in the area enabling the the cell to function better as well as to produce collagen and elastin.