Chemistry of Sunscreens
“Over 400 years ago, Copernicus declared that the sun was the center of our universe. Primitive societies in every continent have worshiped the sun as the god that provided warmth and made the crops grow” Today, the sun is not something we worship but something we try to avoid due to the fact that we are aware that it contains two main sources of ultraviolet radiation that is harmful to our bodies.
Ultraviolet radiation (UVR) is defined by wavelengths, and is divided into different energy levels from shortest to longest wavelength. UVC rays have the shortest wavelength, the most energy and fortunately do not penetrate the atmosphere. UVB rays are the most forceful rays that reach the earth. UVB stimulates the production of new melanin which leads to an increase in the dark-colored pigment within a few days and causes the cells to be stimulated forming a thicker epidermis. UVA activates melanin pigment already present in the upper skin cells and it penetrates into the deeper skin layers, where connective tissue and blood vessels are affected. As a result, the skin gradually loses its elasticity and starts to wrinkle therefore causing premature aging. Although UVB light is primarily responsible for sunburn, UVA light causes tanning, even though it penetrates the skin more than UVB light. Regardless of the effects on the skin, both types of light contribute to premature aging, skin cancer and other types of skin damage.
In the 1960’s and 1970’s recognition was made for the need to block the UV spectrum. Late in the 1960’s one of the first sunscreens appeared but they were not very effective, however, improvements continued to be made. It was around 1979 that the U.S. Food and Drug Administration concluded that sunscreens could in fact help prevent skin cancer and the first rating system for SPFs or sun protection factor was developed to block the very narrow band of UV radiation, which is UVB. Unfortunately it was not...
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