I have dark circles under my eyes. What can I do?

Options. A number of treatments may be helpful but it depends on what the primary cause is. This appearance may be related to puffy lower eyelids and/or volume loss in the tear trough area. Hyperpigmentation and/or prominent blood vessels may also contribute. Typical remedies include lower eyelid lift, fractional co2 laser resurfacing and fat grafting versus injectable filler to the tear trough areas.
Dermal Filler. In most circumstances the dark circles that form under the lower lids are a result of leaky capillaries in the thin skin of the lid. This problem has no predictable solution, though many creams claim to improve this condition. In some cases, the circles are due to a deep indentation at the "tear trough" line between the lid and the upper cheek. Fillers may help to camouflage the shadowing.
Multiple possibiliti. If shadow from puffy eyelid-- surgery hyperpigmentation-- hydroquinone, pharmacologic peel laser, retinoids. Blue vien plexus under thin skin-- reduce nasal congestion, skin care products to thicken skin. Judicious makeup, eyeglasses stay rested and healthy in some cases fat graft may help.
Depends. Often dark circles are due to shadow effect created by bags under the eyes. That can be corrected by surgical removal of the fat bags ( blepharoplasty). If there is no bag then the dark circles are often due to color of blood vessels or plain pigmentation of the skin ( make up can help with these).
Depends on why. Some people (or families) have dark circles under the eyes because the skin there has more color. For women, make-up can help. Some people have darker lower eyelids because of extra blood in the tiny blood vessels in the skin. If this is from allergies or sinusitis, a doctor can treat it. It can also be from fatigue or eye irritation, in which case otc eye drops (for less than 1-2 days) can help.