Your question is not very clear - dull is not quite the same thing as dark, and usually a dull complexion is a minor problem, and one that should not stop you from wearing deep neck or backless dresses. At the same time, there is no reason why the skin on your tummy and back should be darker than the rest of your body either. These parts of the body tend to be covered most of the time, and are therefore least exposed to sunlight. Parts such as the face, neck, and hands are the ones that tend to be darker, as they are exposed to the sun most of the time, and as a result they develop a tan that is effectively almost permanent. If this is your problem, then the solution is quite simple - you need to start protecting your skin from sunlight. First of all, avoid going outdoors during the peak sunlight hours, and if you must go outdoors, ensure that your skin is properly covered. Wear a hat, wear full sleeved tops, and also apply sunscreen generously on the exposed areas.
If, on the other hand, your face, hands and other areas are fair, but your belly and back are dark, then you need to consult a doctor, or preferably a skin specialist about this problem. You may be suffering from some more serious skin problem than a mere tan or poor complexion, and it is better to get this treated by a specialist as soon as possible.
If your problem is simply that your complexion is dull and rough in areas such as your back and belly, and not smooth and glowing like the skin of your face, then you can try some home remedies. However, you should note that the color and texture of the skin is not even all over the body, so your aims should be realistic. First of all, consider whether you need to moisturize regularly - the problem may be mainly due to dry skin. In addition, some amount of regular exfoliation is needed in order to get rid of the dead cells from the surface of the skin. For this, you can start using a loofah daily when bathing. Alternatively, you can use a home made scrub by soaking a tablespoon of oatmeal in milk for an hour or so, and then using the oatmeal to gently scrub your skin. This will achieve both exfoliation and moisturization.
answered by G M