New York, Sep 5 : Scientists have finally decoded why farmers, road crews and others who work long hours outdoors, or someone who spends too much time in tanning booths get the "leathery" complexions.  When skin absorbs more ultra violet (UV) radiation, the collagen fibres in it become more tightly packed together, leading to increased stiffness and tissue that is harder to break, according to the research from Binghamton University. The study, published in the Journal of the Mechanical Behavior of Biomedical Materials, explored how UV radiation can alter the microstructure of human skin. They found that collagen, the fibrous protein that binds together tissue, tendon, cartilage and bone throughout our bodies get particularly affected. This new study builds on previous research that focused on the outer stratum corneum, the top layer of skin. In the new study, the team compared full-thickness skin samples before and after various levels of UV exposure. "One way to characterise the material characteristics of skin is by conducting a mechanical stretch test on it. If it stretches very easily, it's relatively compliant, but if it's much harder to stretch it, you can characterise it as much stiffer. My experiment was to see what the isolated effects of UV light would be and compare it with a scenario where a skin is not exposed to UV light," said lead researcher Abraham Ittycheri, doctoral student at the varsity. "We don't want to put a fear factor in here saying 'don't go out in the sun'. But extended periods of time under UV light can toughen up your skin as well as lead to a higher risk of carcinogenic problems," he added. Our skin is the body's largest organ and the first line of protection against microbes and other outside attacks, so ways to maintain and even strengthen it are clearly beneficial. "Any kind of disruption to the normal process of skin is going to be extremely dangerous and detrimental to our overall lifestyle," Ittycheri said. "That's not even going into the cosmetic side of things, where a person's perception about themselves can be challenged when their skin does not look good.' /IANS