India, May 22 -- As you step out of your house to seek some natural vitamin D, you inevitably also expose your skin to the sun rays, and the harmful ultraviolet (UV) radiation. This may cause sunburn, wrinkles and even skin cancer in extreme cases. That's why using sunscreen is a must. Think of it as a barrier that prevents the harmful ultraviolet rays from reaching your skin and causing damage, says dermatologist Dr Sachin Gupta....