The Science Behind Sunscreens

How do sunscreens work to protect the skin from UV rays? There are two main types of sunscreens. Absorbers and scatterers.

Absorbers

Absorb ultraviolet rays and undergo a chemical change that transforms them into heat and other forms of energy and releases them. This is a chemical method. Substances used in absorbers have a poor reputation, with some reports of absorption into the human body through the skin.

Scattering agents.

Reflects UV rays so that they do not reach the skin. Physical method. Titanium dioxide and zinc oxide are used. These two substances do not affect the human body because they are not taken into the body through the skin. Diamonds are famous for their high refractive index (it is the refraction of light that makes them appear to sparkle), but titanium dioxide has a higher refractive index than diamonds.---

References

• The 50 Minerals That Changed World History, Eric Chaline.
• 日焼け止めはどうして効くの？
• 【酸化亜鉛】と【酸化チタン】 意外と知らない紫外線散乱剤の特徴