The sun is an important source of vitamin D for the body, but it also has some detrimental effects on the body and particularly on the skin. This is probably why the beauty industry is busy in manufacturing so many products that allegedly protect the skin against the harmful effects of the sun.
All of them have sunscreens. They have the added ability to shield, and probably reflect the ultraviolet radiations falling on the skin, usually the face. In some cases, the skin might begin to sag with age, and this is where a sunscreen steps into the picture to help the skin.
Almost all beauty-creams are endowed with a Sun Protection Factor (SPF) element. Basically, SPF is the measure of protection a cream or lotion is able to provide against the harmful ultraviolet rays of the sun. Ultraviolet radiation from the sun is capable of causing sunburn and in the long run, it can even lead to skin-cancer.
The SPF rating recommended by dermatologist or skin specialists all over the world is SPF 15 or SPF 30. A cream with an SPF spelling into higher numerals is not able to deliver any better results. You might consider re-applying the cream after an interval of two hours.
Using a sunscreen becomes all the more important in case of children because they have sensitive skin which is amenable to damage by radiation emitted by the sun.
On the other hand, a regular use of sunscreens is found to reduce free radical formation. Sunscreens don't let sunlight penetrate the skin, and while this can have all the good effects you are looking for, it also hinders the formation of vitamin D in your body, so that you just might develop a deficiency of vitamin D in case you regularly use sunscreens.