. These dark rings can appear without having any underlying disease ,but it can also be related to other conditions like diabetes, being overweight or obese and other hormonal disorders like ovarian cysts.
This condition does not need treatment , however if there is an underlying disease , this condition should be properly treated to control the apparition of these dark rings like topical retinoids, dermabrasion and laser therapy.
Please discuss these treatment options with a dermatologist.
I hope it helps. Take care and please do keep me posted in case you have any additional doubts. Kind regards.