DEAR DOCTOR K: You've said many times that the sun can harm our skin and increase the risk for skin cancer. How does it do that?
DEAR READER: As you age, the single biggest cause of damage to skin is sun exposure. This damage is called "photoaging." Over the years, sun exposure causes fine and coarse wrinkles; baggy skin with a yellow, leathery appearance; and dry, scaly skin. It also reduces collagen, a natural chemical that gives strength to tissues and that supports a network of blood vessels in the skin. As a result, the skin bruises more easily.