To prevent skin cancer and to reduce photoaging, one can make the most impact by limiting sun exposure in childhood. It is also known that melanoma, a potentially fatal skin cancer, is associated with blistering sunburns in childhood. If one is going to be sweating or swimming or otherwise exposed to water, it is very important that the sunscreen be waterproof. Even waterproof sunscreens should be reapplied every two hours while one is out in the sun. There are sunscreens and sunblocks.
Sunblocks block all form of light, and zinc oxide is a good example of a sunblock.
It is a very effective way to prevent sun although people don't like to wear plain zinc oxide. My daughter has small, ring-like dry patches on her body. They don't itch but they look terrible. There are a number of possibilities for dry, ring-like patches on the body. Probably the most common one is a form of eczema.