Dark circles under your eyes can make you look tired or older. While they’re usually harmless, causes can range from lack of sleep and allergies to genetics and ageing. Thinning under-eye skin allows blood vessels to show through, causing a shadow. Hyperpigmentation, especially in people with darker skin tones, can also darken the area. Loss of under eye fat also results in hollowness. While there’s no one-size-fits-all solution, getting enough sleep, and staying hydrated helps.