Critics of sunscreens and sunblocks point out that despite increased promotion and use of sunscreen, the incidence of skin cancer continues to increase. However, this does not mean that sunscreen causes skin cancer. The problem with sunscreen, though, is that many people use sunscreen improperly and have a false sense of security. For example, a person who uses sunblock with SPF (sun protection factor) 50 in the morning may feel that such a strong sunblock will give him/her protection all day so this person may spend more time out in the sun. This is incorrect as the sunscreen and its effects will wear off within several hours so this person will essentially be unprotected from the sun during the afternoon hours, when the sun is strongest. As a result, reapplication of sunscreen every 2-3 hours will provide effective sun protection. So it is the "misuse" of sunscreen that is a problem.
Also, the rate at which skin cancers are increasing is slowing down with increased use of sunscreen. Without sunscreens, there would likely be even more diagnosed cases of skin cancer. It is recommended to consult with your dermatologist regarding which sunblocks would be most appropriate for you as it certainly has been proven that excessive sun exposure leads to skin cancer. Sunscreens that block UVA and UVB will be most effective in preventing skin cancer.
The concept that sunlight is good for us stems from the fact that vitamin D precursors are synthesized in the skin in response to sunlight. There are many known benefits of vitamin D and it certainly is a necessary part of the diet. The amount of sunlight needed for the skin to help in vitamin D synthesis is not very great and even with the use of sunscreens daily, individuals will receive enough sun to the skin for proper vitamin D metabolism. All of the benefits of vitamin D have not yet been defined but a little bit of sun exposure while wearing sunscreen combined with a balanced diet will allow for enough vitamin D to be circulating within your body!
I hope I have a shed a little light on these two ideas which may make one unsure of the benefits of sunscreen. Sunscreens and sunblocks will help prevent sun damage and skin cancer when used properly and should be used as part of a healthy lifestyle.