Dark circles are not harmful, but it can make you look fatigue or older than your age. It can also indicate health problems in the rest of the body. The under-eye skin is one of the most delicate areas in the human body. It also has no oil glands, and that makes it ultra susceptible to dark circles, rings or shadows. Several factors may cause dark circles including heredity, aging, mental or physical stress, hormonal changes, nutritional deficiencies and lack of sleep. Too much sun exposure may trigger your body to produce more melanin, the pigment that gives skin its color, which is also a cause of dark circles. As we get older, the skin gets thinner and losses fat and collagen. This makes the reddish-blue blood vessels under your eyes more obvious. Dehydration and anemia can also negatively influence the under eye skin and lead to formation of dark circles. Certain unhealthy lifestyle and skin habits can also give you dark circles under the eyes. Here are 5 such habits that need to be changed to reduce dark circles under the eyes.