Working out which type you have takes about a minute in front of a mirror, and it is worth doing before you buy anything.
This is where the difference is largest. Pigmented dark circles are considerably more common in brown, South Asian, Middle Eastern and Hispanic skin, often start in childhood or the teens, run strongly in families, and involve genuine extra melanin rather than shadow or vessels. On lighter skin the vascular type dominates and tends to look blue or purple. It matters practically, because the treatments that help pigment are not the treatments that help vessels, and much of the advice online assumes the lighter-skin version.
If what you have does not match any of these, see Lookalikes near the bottom of this page.
"Dark circles" covers four different problems that happen to look similar. They have different causes and genuinely different answers, and most wasted money in this area comes from treating the wrong one. Work out which you have first — most people have a mix of two.
The skin under the eye is the thinnest on the body, and there is very little fat between it and the bone. That is the setup that makes all four causes possible.
Pigmented circles come from extra melanin in the skin. Most of it is genetic — they often start in the teens and run in families — and they are much more common in brown, South Asian, Middle Eastern and Hispanic skin. Pigment can also be left behind by inflammation, so eczema, allergic rhinitis and years of rubbing the eyes all darken the area. Sun exposure deepens it. Vascular circles come from that thin skin letting the blood-filled vessels beneath show through as blue or purple. Anything that dilates those vessels or slows drainage — poor sleep, alcohol, crying, nasal congestion, allergy — makes them more obvious, which is why this is the type that genuinely changes overnight.
Structural circles are different in kind. With age, the fat pads under the eye shift and shrink, the ligament that anchors the tear trough stays put, and a groove forms between them. Bone around the eye socket also thins over time, widening the hollow. What you see is a shadow cast by an actual dip in the surface, so it will not respond to anything applied to the skin. Some people are born with this shape in their twenties. Swelling is the fourth, and it is usually salt, alcohol, allergy, crying, or fluid that has pooled overnight.
These help pigment and skin thickness, slowly and modestly. None of them will change a hollow or a shadow, so check which type you have before you spend.
Dark circles are cosmetic, so a visit is optional. It is worth going if:
What the visit gets you: a straight answer on which type or combination you have, tested by stretching the skin and changing the light; a prescription option if pigment is the driver; and, if you want filler, an injector who understands the anatomy in an area where mistakes are visible and occasionally serious.
Prescription options here are aimed squarely at the pigmented type. They do nothing for vessels or hollowing, and eyelid skin is thin enough that irritation is easy to cause.
The only category that addresses a structural hollow. It is also where the real risks are, and where who performs it matters more than the technology used.
Allow three months. The change is real but modest — a shade or two, not a transformation. Stopping usually means it drifts back.
Days. If your circles improve markedly after a good week's sleep, you have the vascular or puffy type, and that is useful information.
Result is visible immediately, settles over two weeks. Swelling and bruising for a few days are normal. Lasts roughly 9 to 18 months. A lumpy or puffy result can be dissolved with an enzyme injection, which is a real advantage of hyaluronic acid filler.
Three to six sessions over months, then gradual fading. In darker skin these carry a genuine risk of making pigmentation worse, so gentler settings and slower courses are standard.
Bruising and swelling for two to three weeks, full settling over months. The result is long-lasting, and it is the option that addresses shifted fat pads properly.
Pigmented circles improve but rarely clear, and they come back if you stop. Vascular circles fluctuate with sleep and health for life. Hollowing is progressive with age, so filler is maintenance rather than a fix. Nobody achieves the under-eye area of a lit and edited photograph, and a good deal of the market runs on the belief that they might.
Dark circles themselves cause no medical problems. The complications here come almost entirely from treatment.
A few things get labelled dark circles when they are something else.