As you have said that you do smoke so these patches can be either due to nicotin pigmentation or can be excessive melanin
pigmentation of the cells as we see on our body surface(moles
). Are they present from the time of your birth? Are they growing in size? Keep observing and keep a note of the size of the patches. If they are growing slowly or rapidly it is a cause of concern. Try to quit smoking
and follow a healthy lifestyle.