Almost everything sold for dark circles is sold as though there is one condition called "dark circles". There are at least three, they have different causes, and a product built for one will do essentially nothing for the others.
Working out which you have takes a mirror and about two minutes, and it is the single most useful thing you can do before spending money.
The three types
1. Pigmented
Actual melanin deposited in the skin. It looks brown rather than blue or grey, has a reasonably defined edge, and it stays much the same regardless of the light or the angle of your face.
Common causes are genetics — it is markedly more common in people with South Asian, Middle Eastern, Mediterranean and East Asian heritage — plus sun exposure, and post-inflammatory pigmentation after eczema, allergies, or persistent rubbing.
2. Vascular
Not pigment at all. The skin here is thin enough to be semi-translucent, and what you are seeing is the network of veins beneath showing through. It reads blue, purple, or occasionally reddish rather than brown.
It gets worse with tiredness, dehydration, alcohol, salt, and anything else that affects fluid and circulation — which is why it fluctuates day to day in a way pigment never does.
3. Structural
A shadow, cast by a genuine hollow. Volume loss under the eye creates a dip, and overhead light turns that dip into a dark band. There is no pigment and no visible vessel — just topography.
This is the one that changes dramatically with lighting, and it is covered in more depth in our piece on hollowing.
Plenty of people have two of these at once, or all three. That is normal, and it is why a single product rarely resolves the whole picture.
How to tell which you have
Go to a mirror in decent daylight, not bathroom downlights.
The stretch test. Gently pull the skin at the outer corner sideways, flattening the area. If the darkness stays put and stretches with the skin, it is pigment. If it fades noticeably as the skin flattens, it is vascular or structural.
The tilt test. Face a window and tilt your chin up so light hits the area directly from the front. If the darkness largely disappears, it is a shadow — structural. If it persists in flat frontal light, it is pigment or vascular.
The press test. Press very lightly on the darkest part for a couple of seconds and release. Vascular darkness blanches briefly and then refills. Pigment does not change at all.
The morning test. Compare first thing after waking with the same area at 6pm. Vascular circles are usually worst in the morning and improve as fluid redistributes through the day. Pigment is stable. Structural shadow tracks the lighting, not the clock.
What actually works for each
Pigmented
Tyrosinase inhibitors — azelaic acid, tranexamic acid, vitamin C, and hydroquinone where it is available to you. Daily SPF is non-negotiable, because UV drives further deposition. Expect three months minimum.
Critically: stop whatever is causing the inflammation. If you rub your eyes because of hay fever, treating the hay fever will outperform any cream.
Vascular
Caffeine gives genuine but short-lived vasoconstriction — useful before an event, not a fix. Vitamin K has thin evidence. Anything that thickens the skin over time, particularly retinoids, helps by making it less translucent.
Sleep, hydration and reducing salt and alcohol have a bigger effect here than on the other two types, which is why this is the version that responds to "get more sleep" and the others don't.
Structural
Topicals can improve skin quality around the hollow but cannot fill it. Products aimed at supporting collagen are the realistic route. Beyond that, it is a procedural conversation.
Why this matters commercially
Most eye products in this category are formulated for one type and marketed to all three. A caffeine serum sold to someone with pigmented circles will do nothing, and they will conclude eye creams don't work — when actually they bought the wrong tool.
Work out your type first. It will save you more money than any discount code.
The short version: stretch the skin and tilt your face at a window. Darkness that stretches with the skin is pigment. Darkness that vanishes in frontal light is shadow. Darkness that blanches under pressure is blood vessels. Buy accordingly.