Why does my skin get a greyish undertone on the areas not exposed to sunlight?

These areas include my chest, stomach, and legs, which I rarely or never show in public. I thought it was just due to a buildup of dead skin, but even when I exfoliate regularly my skin gets this greyish undertone. It doesn%26#039;t happen to my face or arms, so is it due to a lack of sun exposure? If so, how much sun should I get to remedy this?|||That would be a question for someone that works or owns a tanning salon. That is one of the questions they ask you on their questionnaire before tanning for the first time. Good luck