The radiant solar energy is mainly responsible for the continued existence on Earth. Although the benefits of solar energy is known since ancient times, it was only during the 19th century that the therapeutic benefits of solar radiations were being understood on a scientific basis and particularly in the treatment of rickets. It was John Ritter in 1808, who discovered the ultraviolet region in solar spectrum. Later Neils Finsen, a Danish Physician discovered the importance of ultraviolet component of sunlight. Finsen was awarded Nobel Prize in 1903 for medicine for his work. He developed UV-B lamp that was very effective in curing Lupus vulgaris, tuberculosis of skin. It was him who stressed that ultraviolet radiations were responsible for sunburn and not the radiant heat.
UV – R is in fact a class of electromagnetic waves of various wavelengths ranging from 400 nm to 100 nm. The UV – R region lies between the visible light rays and X-rays of electromagnetic spectrum.
Types of UV Rays
UV-R is mainly classified in three spectral regions,
- UV-A : These are long waves and can penetrate the atmosphere more deeply than the other two. They have wavelength 315 to 400 nano metres.
- UV-B : These are middle waves having wavelength between 280 to 315 nano metres.
- UV-C : These are short waves having wavelength between 100 to 280 nano metres. They do not penetrate into the atmosphere and got absorbed by ozone layers.
Benefits of UV Exposure
We all have read about the risks of UV exposure like skin cancer, sun burn, sun tan, skin ageing, blistering and pain, eye problems etc but here I am going to discuss the benefits of UV Exposure.
1. Vitamin-D Formation
The skin absorbs UV-B radiation of sunlight to convert sterol precursors such as 7-dehydrocholesterol to vitamin D. This vitamin D is further transformed by the liver and kidneys to biologically active metabolites such as 25-hydroxy vitamin D. These metabolites then act on the intestinal mucosa to facilitate calcium absorption and on bone to facilitate calcium exchange. This furthur helps in skeleton development and blood cell formation. It has been recognised that children which are chronically under exposed to adequate amount of solar UV rays may develop rickets, a deforming disease characterised by under mineralization of bones. The disease can be cured by exposure to natural or artificial sources of UV rays incorporating wavelength less than 315 nm. Sub-erythemal doses of UV-B rays ate sufficient for the satisfactory synthesis of vitamin D.
2. Germicidal Lamp
It is low pressure mercury discharge lamp where more than 90 percent of radiant energy occurs at a wavelength of 254 nm. The remaining energy is distributed among the mercury lines in the UV-B, UV-A and visible regions which gives the lamp pale yellow glow on operation. The use of this lamp in medicine is for sterilization of air and water, as it helps in preventing the growth of moulds and bacteria. But since its radiations are highly reactive to eyes and skin, therefore these lamps should not be viewed directly.
3. Treating Psoriasis
The most widespread use of UV radiations in clinical medicine is in treatment of psoriasis, a common skin disease which produces sores and scaling of skin. It is a disease where your own immune system attacks your cells. For this photochemotherapy treatment is done which involves administration of a photo active drug followed by exposure of the patient to UV-A radiation.
4. Healing Ulcers
Indolent ulcers begin to heal in about 5 to 7 days followed by UV-R irradiation. UV irradiation of ulcers is of considerable importance and has been practiced in physiotherapy for several years. The success of treatment relies on the bactericidal properties of UV radiations and for this reason it is very important that the lamp must emit UV-C radiations.
Chilblains results from exaggerated response to cold in which the blood vessels of the skin contract so much that the skin is deprived of blood and oxygen. It causes swelling, itching and a characteristic burning sensation usually confined to fingers and toes. Actinotherapy-The treatment using artificial UV-R sources is done whose aim is to achieve repeated first degree erythema on the affected parts in order to stimulate blood supply.
6. Treating Neonatal Jaundice
Neonatal Jaundice is a common disorder found in about 60 percent of new-born babies within first week after their birth. But if it is left untreated, the condition may lead to permanent brain damage. Phototherapy immensely helps in the treatment of neonatal jaundice. If it is not severe the baby is advised to be exposed to sun light for considerable time period. The wavelength of light used in treatment is 400 to 480 nm.
7. Polymerization of Dental Resin
The restoration of pits and fissures in both deciduous and permanent teeth is often accomplished by using an adhesive resin polymerised with UV-A. The resin is applied to the surface to be treated with a fine brush. It is then hardened by exposure to UV-A radiations for about 30 seconds. It offers greatest protection against tooth decay at the sites of pits and fissures.
A socially desirable consequence of exposure to unfiltered sunlight is the delayed pigmentation of the skin known as tanning. It becomes noticeable about two days after exposure and gradually increases for several days. Tanning is not only due to the formation of new melanin but also due to migration of pigment already present in the basal cells to the more superficial layers of the skin. Studies have shown that the thickening of the epidermis that occurs after mild exposure to UV-R can also afford protection against damage caused by UV-R .
Although there are benefits of UV Exposure but its ill effects can not be ignored. So, it is up to you how you take care of yourself and how much exposure is needed. Over exposure to sun should be avoided and preventive steps must be taken before going out in sun.