What causes dark circles under the eyes?

Dark circles under the eyes (DC) are defined as bilateral, round, homogeneous pigment macules on the infraorbital regions. Despite its significant prevalence, there are a few published studies about its pathogenesis. DC are caused by multiple etiologic factors that include dermal melanin deposition, postinflammatory hyperpigmentation secondary to atopic or allergic contact dermatitis, periorbital edema, superficial location of vasculature, and shadowing due to skin laxity. The purpose of this review is to discuss some of the available evidences about the anatomic features that could explain dark circles and the proposed treatments for this unpleasant condition.