Compare the area in two kinds of light
Look in indirect daylight and then under a ceiling light. Overhead light can exaggerate shadows from hollows or puffiness. Pigment can remain visible under both. Several causes often overlap, so lighting is one observation you can bring to a consultation.
Think about itching and rubbing
Allergies or irritation can contribute to darkness and make you rub the area more often. Ask a pharmacist or GP about ongoing irritation before adding stronger skincare around your eyes.
Ask what the treatment can realistically change
A product aimed at skin quality, treatment for irritation and an assessment of under-eye hollows answer different questions. See your GP for new, persistent discolouration or swelling that affects just one eye.