Sun rays contain both ultraviolet A rays (UVA) and ultraviolet B rays (UVB). UVB rays affect superficial layer of the skin causing skin darkening. UVA rays penetrate deep into the skin and causes damage to the inner layer of skin causing wrinkles and change in texture texture over a long period of time. 

One must protect the skin to prevent skin darkening, any pigmentary changes, and ageing of the skin. 

This can be done by avoiding direct sun exposure during peak sun hours. Wearing protective clothing whenever going out in sunlight. Apply a good sunscreen which has high SPF of 30 or more and which protects against both UVA and UVB rays.

Sunscreen should be applied 15-20 minutes before going out in sun. It should be applied repeatedly every 2-3 hourly. For kids a physical sunscreen would be better. Re-apply sunscreen after swimming or exercising. Preferably use water resistant sunscreen for beach or pool activities. Sunglasses with UV protection should be used. There are lipstick sunscreens available for lip protection. 

Sunscreens are available in cream, lotion and gel base. There are physical and chemical sunscreens. They can be water proof or water resistant. Depending upon the skin type, sensitivity, location, climatic condition, activity one can choose from the variety that is available in the market.