Greetings. It is normal for most people to darken by a couple of shades in their teens and early twenties, but many of them regain some of their color as they get settled in more 'indoor' jobs. Largely our acquired colour depends on our sun exposure and on our exposure to pollution, etc (you must have noticed - skin looks clearer after a long holiday to a not so polluted city/country). Apart from these, there may be other causes of pigmentation - as a part of photoageing/hormonal changes/vitamin deficiencies/ so on and so forth. The pattern of change of skin tone gives the dermatologist an insight into cause of your pigmentation. So just lightening creams may not be the ultimate solution. See a qualified dermatologist near you. Warm regards