Phototherapy is the use of natural or artificial light for the treatment of certain physical or psychological illnesses. Light is the visible part of the electromagnetic spectrum. The human eye perceives each wavelength as a different colour. The wavelengths just above red are called infrared rays, and those below violet are the ultraviolet rays. Both rays are invisible to humans, but are part of phototherapy.
The infrared rays produce warmth and promote circulation. They are used to calm pain and to heal wounds.
The visible light has been successfully used to treat acne, jet-lag and the seasonal affective disorder, among other ailments. Recent studies show that depression not associated to seasonal changes also improves with phototherapy treatment.
According to the problem to be treated, sessions using different types of light sources can be prescribed: fluorescents, LEDs, dichroic lamps, blue, red or white light, as well as laser.
In small doses, the ultraviolet rays types A and B (known as UVA and UVB) are beneficial for fighting psoriasis and other problems. Everyone is aware, however, that if these rays are abused they can damage the skin and cause cancer.
Balneotherapy is characterised by the application in general of naturist techniques. Therefore, the doctors at these centres generally prefer sunlight to artificial light, whilst in spas it is more common to find light and electromagnetic wave production equipment.
The ozone layer in the atmosphere prevents UVC rays, which are particularly damaging, from entering. Pollution is reducing the thickness of this layer and therefore it is necessary to use sun protection creams when sunbathing.
The ultraviolet rays contribute to the production of vitamin D, vital for the correct functioning of the body. In countries in high latitudes, where during certain seasons there are few hours of sunlight, it is common to have sessions of artificial light, using the appropriate eye protection.