What appears to be dark circles under your eyes are sometimes just shadows cast by puffy eyelids, or hollows under your eyes that develop due to loss in muscular and bone mass, which is a normal part of ageing.
as we age, our skin loses its elasticity and ability to regenerate, and becomes thinner. being the thinnest and most delicate part of the facial skin, the skin around your eyes (called periorbital skin) will be the first area to manifest signs of ageing and fatigue. the periorbital skin is on average about 0.5 mm thick compared to an average of about 2 mm thick on the rest of your body. the reddish-blue blood vessels under the eyes become even more prominent with age due to the thinning of the epidermis (skin surface) that results with the slowdown in production of collagen and fats.
Prolonged and excessive exposure to uv rays prompts your body to produce more melanin, the pigment that gives skin its colour. Areas of the skin where there is increased melanin production will become darker.
Dark eye circles can run in the family. Some people are genetically predisposed to having thinner skin below the eyes, or periorbital hyperpigmentation – a condition in which more melanin is produced by the skin below the eyes, resulting in it appearing to be a darker colour. Periorbital hyperpigmentation is more prevalent in darker-skinned people, especially those of Asian and African origins.
Lifestyle factors and medical conditions leading to fluid imbalance or local swelling can result in puffy or swollen eyelids, which cause shadows that make the area under the eyes appear darker. These include lifestyle factors (such as drinking too much coffee), chronic dehydration, anaemia, head or facial trauma, and allergies.