There are various reasons for dark circles under the eyes and most of them aren’t something that can’t be treated topically with an eye cream despite what the skincare industry would have you believe.... What is your skin tone? Darker skins are more prone to this - pigmentation. Ensure you wear sunscreen around the eyes to minimise as much as poss.
Do others in your family have the same issue? It can also be a family trait which unfortunately you can’t do a great deal for.
Are you a big eye rubber? Or rub your eyes to remove make-up a lot. You can drag the skin by doing this causing skin damage and inflammation. Try not to rub at your eyes.
It can be a loss of fatty tissue or age related, the shadow can cause a darker look, you can have fillers to plump the areas up.
Some people swear by facial massage, with jade tools also to improve the overall tone of the skin.
Really, If you’re getting enough sleep, have a good diet, take care of your skin in terms of hydration, spf, not rubbing etc it probably is something you’re just prone to and you’re best to try to visually minimise with a colour corrective, light reflective cosmetic.
Nicola Chapman was having some kind of treatment or filler or some specialist derma treatment as she suffers, I don’t think it made a higher amount of difference but I believe he has videos on it