By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) - The risk of developing skin cancer is increased by exposure to sunlight. Sunblock can help protect against it but it is not one hundred percent. Ultimately it comes down to common sense.

If you are going to be out in the sun for an extended period of time, you should wear loose fitting clothing as well as a wide brimmed hat. Another key point to think about is the fact that sunblock needs to be reapplied after swimming or exercising.

Many people also tend to be stingy with sunblock. They figure if they use just a little of it, the sunblock will last longer. Remember it does not do you any good if it stays in the bottle.

One final point is that you can’t build a base tan to protect against skin cancer. You need to consistently worry about skin cancer.