Dark circles, clinically known as “periorbital hyperpigmentation”, can be differentiated according to the etiology and clinical manifestations, including pigmented, vascular, structural and mixed types. 1. Pigmented type: this type is caused by increased pigmentation, manifested as gray or brown periorbital skin and aggravated by fatigue and poor sleep in some patients. 2. Vascular type: This type is caused by blood stagnation around the eyes or thin skin of the lower eyelid, which is characterized by the prominence of blue blood vessels, which are most obvious on the inner side of the lower eyelid. 3. Structural type: This type is caused by the protrusion of bony structures in the face or the aging and relaxation of the periorbital skin, which produces shadows in non-frontal light and gives a dark circle-like appearance. 4. Mixed type: Any two of the first three types are superimposed or all three types are present at the same time.