New research in Australia confirms the advice of many dermatologists to their patients - to avoid the aging effects of the sun on your skin, use sunscreen. While the benefits of sunscreen are well known when it comes to preventing sunburns and lowering the risk of skin cancer, researchers said rigorous studies were previously lacking on how sunscreen use affects the signs of skin aging, or photoaging. Photoaging happens after long-term exposure to ultraviolet radiation, which penetrates the skin and can cause collagen to break down and DNA to mutate. Long term effects of photoaging include wrinkles, leathery skin tone, loss of the skin's elasticity and spider veins. The new study, conducted at the Queensland Institute of Medical Research analyzed data from 903 adults younger than 55 who were followed between 1992 and 1996. Half of the participants were instructed to put sunscreen of SPF 15 or greater on their head, neck, arms and hands every morning, and to reapply when necessary. The other half used sunscreen according to their own discretion. At the start and end of the study, the researchers measured photoaging using the skin on the back of each person's left hand. The researchers found that over four years, the skin condition of people who were told to use sunscreen daily evidenced no detectable changes, once other sun-related factors were taken into account. Beta carotene, which was also given to some of the participants, did not seem to have any protective effect on skin aging, however.