Eczema (atopic dermatitis) is a chronic inflammatory skin condition characterized by dry, itchy, and irritated patches. Hyperpigmentation refers to the common darkening of the skin that occurs when excess melanin is produced and deposited. Eczema is a frequent cause of skin darkening, which appears in the areas where the initial inflammation or rash occurred.
The Link Between Eczema and Dark Spots
The darkening that follows an eczema flare is classified as Post-Inflammatory Hyperpigmentation (PIH). This type of hyperpigmentation is a direct response to injury or inflammation in the skin, distinguishing it from sunspots or hormonal darkening like melasma. The intense itch and chronic inflammation associated with atopic dermatitis make PIH a common trigger. The dark spots represent the skin’s healing process after the active eczema rash has subsided.
The hyperpigmentation occurs precisely where the skin was inflamed, scratched, or traumatized by the condition. While the initial eczema lesion heals quickly, the resulting dark spot can linger for a significantly longer period. This lingering discoloration can sometimes be a greater concern for patients than the initial rash itself.
How Inflammation Triggers Pigment Production
The mechanism begins when chronic inflammation and mechanical trauma from scratching damage the skin’s epidermal barrier. This damage prompts the release of pro-inflammatory signaling molecules, such as cytokines and chemokines, into the skin tissue. These mediators stimulate melanocytes, the specialized cells responsible for producing skin pigment.
The overstimulated melanocytes initiate an excessive production of melanin, a process called melanogenesis. This surplus melanin is transferred to surrounding skin cells in the epidermis, resulting in visible darkening. In cases of severe inflammation, the basal layer separating the epidermis and dermis can be damaged, causing melanin pigment to drop into the deeper layer of the skin, where it is trapped by immune cells called melanophages.
Identifying Eczema-Related Darkening
Eczema-related PIH appears as flat patches or macules that match the distribution of the previous eczema flare. The color of the patches varies widely, often presenting as shades of brown, gray, or blue-gray, depending on the depth of the melanin deposition. Epidermal PIH appears brownish, while deeper, dermal PIH tends to have a more blue or gray hue.
Individuals with naturally darker skin tones (Fitzpatrick skin types IV through VI) are more susceptible to PIH. Their melanocytes are more reactive and produce higher baseline levels of melanin, leading to more intense and longer-lasting dark spots following inflammation. In these individuals, the active eczema rash may not appear red but rather as purplish, grayish, or darker brown patches, which can sometimes lead to underestimation of the condition’s severity.
Strategies for Reducing Hyperpigmentation
The most effective strategy for minimizing PIH is to manage the underlying eczema to prevent inflammation and stop the cycle of scratching. Controlling the itch and treating the active flare with prescribed anti-inflammatory medications reduces the trigger for excess melanin production. This limits the initial damage that begins the darkening process.
For treating existing dark spots, daily use of a broad-spectrum sunscreen with a high Sun Protection Factor (SPF) is necessary, as UV exposure darkens existing PIH. Topical ingredients can help lighten the spots by interfering with the pigment production pathway. Gentle options like Vitamin C, niacinamide, and azelaic acid can be used to fade epidermal pigmentation over time. Prescription treatments, such as hydroquinone or topical retinoids, may be recommended by a dermatologist for stubborn cases. While the initial eczema rash heals quickly, PIH fades slowly, often taking several months or even years to fully resolve.