Sunscreen Chemistry

Throughout time we have used natural and chemical ingredients to prevent skin damaged including sunburn, aging, and cancer as seen in early journals of European explorers and naturalist alike. They recorded their experiences of seeing indigenous people used mud, sand, oils, berries to paint their skin and protect it from the harsh rays of the sun. Although they may not have known that it was ultraviolet light radiating from the sun that was causing their symptoms; we have an innate response to protect ourselves.

The sun produces all wavelengths of visible and non-visible light. When looking at the damaging effects of sun on skin, we more closely need to inspect the ultraviolet region of the electromagnetic spectrum. The UV region is split into three major subcategories; UVA, UVB, and UVC rays. The UVC is the most dangerous radiation; however, nearly all of it is blocked by our ozone. UVB and UVA rays cause sunburn, skin aging and most severely DNA dysfunction. 

Although the sun can cause many aliments, UV rays are extremely important to a healthy functioning body. Vitamin D, which can not be produced by the body, is synthesized by the photolysis of a steroid in the deep epidermis of the skin. Without the exposure to natural light, the biochemical mechanism will not pursue causing disorders in both children and adults including rickets, ostomalaica, and osteoporosis. 

Although we do need UV rays to produce vitamin D, we as Americans overexpose ourselves. The National Cancer Institute stated that depending on skin tone and sensitivity most people only need ten to fifteen minutes of exposure a day. When does that actually happen during the summer? Because we tend to stay out twenty to thirty times longer than the recommended we need some level of protection to lessen the chances of skin damage. 

The first, very crud, sunscreen was introduced in 1938 by an Austrian chemist. Again necessity spurred his interest in the production of the product. It was said that he was hiking up a mountain and got severely burned. Later that year, sunscreen was born. Sunscreen is a chemical blocker, unlike sunblock which is a physical blocker, absorbs UV radiation at specific wavelengths of light.

There are many inorganic and organic molecules that are put in sunscreens today. By incorporating more than one type of molecule, manufactures can market their product as a broad band spectrum, meaning that it covers a large range of UVA and UVB rays. But how does it actually absorb and scatter the radiation?

One of the most common organic molecules used in sunscreens is para-aminobenzoic acid, also know as PABA. It is in the B-complex vitamin family. The body can make PABA from folic acid. PABA can be made by the body it not truly a vitamin. The mechanism which allows PABA to absorb UV radiation is due to the resonance of the molecule. Resonance can be explained by saying that many molecules have more than one possible way in which the valence electrons could be placed. These electrons move freely across many nuclei. In PABA, a carbonyl group, a functional group where a carbon is double bonded to oxygen, can produce resonance by moving the valence electrons.  The shift or movement of the electrons closely matches the frequency of UVB light, absorbing the light energy and releasing it as heat and or longer wavelengths of light

Resonance of carbonyl group on PABA

Discovery of Sunscreen
Sunscreen Verses Sunblock
Vitamin D Synthesis
Portrait of the Sun
Active Ingredients
Skin Cancer
Ultra-Violet Radiation
Want to Learn More?

Lesson Plans