Dark Circles: Is Cortisol Really the Cause, or Is It Genetics and Sleep?

Dark circles under the eyes get folded into "cortisol face" content constantly, usually with the explanation that stress hormones thin the skin and dilate blood vessels, making shadows more visible. It's a plausible-sounding story. It is also, per the dermatology literature on periorbital hyperpigmentation, not the explanation dermatologists actually reach for first.

The dominant driver, according to a widely cited comprehensive review in the Journal of Clinical and Aesthetic Dermatology, is genetics. Periorbital hyperpigmentation is described as having a strong hereditary component, more common in people with darker skin tones, and often present from a young age, well before any sustained stress exposure could plausibly explain it. The skin under the eyes is also simply different from skin elsewhere on the face: it is thinner, with less supporting fat, so the blood vessels and muscle underneath show through more easily in some people regardless of stress levels.

Aging changes the picture through structural mechanisms unrelated to hormones. As skin loses collagen and fat volume over time, a hollow called the tear trough can develop, and skin also grows more lax, both of which cast a literal shadow that reads as a "dark circle" but is really more of a contour issue. Clinical reviews on treating infra-orbital dark circles group cases into distinct types, vascular, pigmented, structural, or shadow-based, precisely because the causes and appropriate treatments differ so much depending on which is at play, which further undercuts the idea that a single hormone explains every case.

Allergies are another well-documented, non-hormonal cause: nasal congestion from allergic rhinitis increases blood pooling around the eyes, sometimes producing the darkened, faintly bluish look Mayo Clinic describes as "allergic shiners." Sun exposure increasing melanin production in already-thin under-eye skin is a separate, independently documented contributor, and unrelated to stress hormones as well.

So where does stress actually fit in? Mostly indirectly, and mainly through sleep. Poor or insufficient sleep is well established as a contributor to under-eye darkness and puffiness, and stress is one of the most common reasons sleep gets disrupted in the first place. That is a real, if two-step, connection. What is not established in the literature is a direct, controlled demonstration that elevated cortisol itself measurably darkens periorbital skin in otherwise healthy people. The specific claim that cortisol thins under-eye skin and dilates vessels, common in wellness content, extrapolates from general stress-skin physiology rather than resting on a study that tested dark circles specifically, which is a meaningfully different kind of evidence.

In practice, that means the fixes with the best support are the unglamorous ones: treating the underlying cause. Antihistamines or allergy management for allergic shiners, sun protection and topical retinoids or vitamin C for pigment-related cases, fillers for volume-related shadowing, and consistent sleep for the fatigue-related component. Managing stress is a reasonable, generally healthy thing to do, but it is better understood as supporting better sleep than as a direct fix for a hormone supposedly staining the skin under your eyes.