Sunburns and suntans are both caused by UVB waves. At first contact, the skin immediately reddens. Then, somewhere from 4-24 hours later, a burn will appear. Burns range in severity, but are identified as a patch of redness that can be itchy or feel hot, among other symptoms. It will eventually peel. Suntans begin to happen usually after 2-3 days. This is after your skin has begun to build up a resistance and begins to tan, protecting the skin underneath. The skin also thickens to protect the other layers of skin. However, important information to know is that both sun tans and sun burns are really just skin damage. This can cause problems later in life such as wrinkles, premature aging, and even cancer.