Darkness because of friction and shaving. Do I need to treat it or will it go away on its own?

1-I have darkness between my breasts and private area and inner thighs since I'm overweight and it causes friction, I'm currently losing weight will the darkness go away on its own or do I need to treat it? What to use to make the friction and darkness lessen? Powder or Vaseline? 2-I also have darkness around my mouth because of dryness and I started shaving because I want to do laser and the shaving made it even darker than before. Will moisturizing fix this? Or do I need to treat it as well?

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