Sunlight consists of visible and invisible rays. Ultraviolet rays, both UVA and UVB, are invisible and present throughout the day, even on cloudy days and indoors. Overexposure to either can cause skin cancer. In addition, UVA rays (or ageing rays) can cause premature skin ageing characterized with wrinkles and age spots, and can pass through windows; whereas UVB rays cause sunburn and are blocked by windows.

Sunscreens are designed to protect against UVrays. There are two types; chemical and physical sunscreens.

Chemical sunscreens contain one or more of the following active chemical filters such as oxybenzone, avobenzone, octisalate, octocrylene, homosalate, and octinoxate which act like a sponge. It absorbs UVrays before it hits your skin. They rub easily into the skin without leaving a white cast.