Psoriasis is a chronic inflammatory condition driven by an overactive immune system that accelerates the life cycle of skin cells, leading to the formation of thick, scaly plaques. While successful treatment reduces the characteristic inflammation and scaling, the affected skin often retains residual marks once the flare has cleared. These marks are a common source of concern for patients, who often wonder if they are permanent scars. Understanding the nature of these residual skin changes is necessary to manage expectations regarding their long-term visibility.
Differentiating Scars from Discoloration
The marks that remain after a psoriasis plaque resolves are typically not true scars, which involve permanent damage and fibrous tissue changes in the deeper layers of the skin. True scarring is rare in psoriasis and usually only occurs if the plaques were subjected to severe trauma, such as aggressive scratching, or if a secondary infection developed. The vast majority of residual marks are instead pigment alterations resulting from the intense inflammation that occurred in the skin.
These pigment changes are classified into two main types: post-inflammatory hyperpigmentation (PIH) and post-inflammatory hypopigmentation (PIHpo). PIH presents as darker patches due to the inflammation triggering melanocytes, the pigment-producing cells, to create an excess of melanin. Conversely, PIHpo manifests as lighter or white patches where the severe inflammation has damaged or destroyed the melanocytes. This leads to a localized reduction or absence of melanin production.
The Natural Timeline for Fading
The body possesses a natural mechanism to resolve these pigment changes over time, slowly restoring the skin’s original color. This process involves the gradual turnover of skin cells containing excess melanin or the slow repopulation and reactivation of melanocytes. The time required for this natural fading is highly variable, depending on the severity of the initial inflammation and an individual’s skin tone.
For many people, especially those with lighter skin tones, hyperpigmentation may fade spontaneously within a few months. However, in individuals with darker skin tones, PIH is more common and tends to be more persistent, often taking six months to over a year to resolve. This is because the inflammatory response deposits more pigment, making the marks more noticeable and longer-lasting. Post-inflammatory hypopigmentation, while less common, can be more challenging, as the loss of melanocytes can be permanent in some cases. Even when temporary, repigmentation can be slow and may take many months to occur naturally.
A significant factor influencing the timeline for fading is exposure to ultraviolet (UV) light. Sun exposure stimulates the melanocytes to produce even more pigment, which can significantly darken and prolong the visibility of hyperpigmented areas. Protecting the affected skin from the sun using broad-spectrum sunscreen is necessary to prevent the marks from becoming darker. Conversely, sun exposure can make hypopigmented areas stand out more clearly against the surrounding tanned skin.
Medical Strategies to Speed Up Resolution
While the body can resolve pigment changes naturally, several medical strategies can accelerate the fading process. The most effective approach is the aggressive management of the underlying psoriasis to prevent new flares and subsequent marks from forming. Early and sustained control of the inflammatory disease is the primary preventative measure against pigmentary changes.
Treating Post-Inflammatory Hyperpigmentation (PIH)
For PIH (dark spots), topical agents are often the first line of intervention. Ingredients like hydroquinone work by inhibiting the enzyme tyrosinase, which is necessary for melanin production. Topical retinoids, such as tretinoin or tazarotene, help by increasing the rate of skin cell turnover, which speeds up the shedding of pigmented cells. Other beneficial topical compounds include azelaic acid and vitamin C, which possess pigment-lightening properties. If topical treatments are insufficient, a dermatologist may recommend in-office procedures, such as superficial chemical peels or specific laser treatments.
Treating Post-Inflammatory Hypopigmentation (PIHpo)
Treating PIHpo (light spots) is often more difficult, as stimulating pigment production is complex. Strategies focus on encouraging the migration and proliferation of residual melanocytes. Phototherapy, particularly narrowband UVB or an excimer laser, can be directed at the white patches to stimulate repigmentation. Topical calcineurin inhibitors, like tacrolimus, are sometimes prescribed off-label to help create a more favorable environment for melanocyte activity. Patients should be prepared for the fact that hypopigmentation is generally the most resistant form of post-inflammatory change.