Psoriasis is a chronic autoimmune condition where the immune system signals skin cells to grow at an accelerated rate. This rapid turnover causes skin cells to accumulate on the surface rather than shedding normally. Scalp psoriasis is a very common localized manifestation, affecting up to 80% of individuals with psoriasis. Understanding the specific visual characteristics of the lesions is the first step toward accurate identification.
The Hallmarks of Scalp Psoriasis Appearance
Scalp psoriasis typically presents as thick, raised patches of inflamed skin called plaques. These plaques are well-demarcated, meaning they have a clear, distinct border separating the affected skin from the healthy skin. The appearance of the underlying inflamed skin varies depending on skin tone. On lighter skin, plaques often appear pink or red, while on darker skin tones, they may be darker red, purple, or brown.
A defining visual characteristic is the presence of scale covering these plaques. This scale is characteristically silvery or white, dry, and has a powdery texture. Unlike the fine, loose flakes of mild dandruff, psoriatic scales are often thicker, more adherent, and can build up into dense, crusty layers. In severe cases, this buildup can resemble overlapping roof tiles.
The scales are formed by the accumulation of skin cells that matured too quickly, piling up on the surface instead of being shed. If these thick scales are picked or scratched off, the underlying skin may bleed in pinpoints, known as the Auspitz sign. This underlying skin is often dry and can be intensely itchy or feel like it is burning.
Common Locations and Spread Patterns
Scalp psoriasis can affect the entire head, but it often favors specific, localized areas. The condition frequently appears along the hairline, where it may extend onto the forehead. This extension beyond the hairline is a typical feature, sometimes referred to as the “corona psoriatica.”
Other common sites for lesions include the nape of the neck and the skin around the ears. The patches can be found symmetrically on both sides of the scalp or concentrated in one area, such as the back of the head. The presence of hair complicates the visual presentation by trapping the shedding scales.
The hair itself usually remains intact, but thick plaques can sometimes cause temporary, localized hair loss. This hair loss is typically due to the trauma of scratching or the difficulty of removing the thick crusts, rather than the disease process itself. The scalp is considered a high-impact site because of its visibility and the difficulty of applying topical treatments through the hair.
Distinguishing Features from Other Scalp Issues
Differentiating scalp psoriasis from other common flaky scalp conditions is crucial, as misidentification can delay proper treatment. Dandruff, known medically as Pityriasis Simplex Capitis, is the mildest form of scalp flaking. Dandruff flakes are finer, white, and loose, lacking the underlying inflammation and thick, adherent plaques seen in psoriasis.
Psoriasis must also be distinguished from seborrheic dermatitis, which is a more inflammatory condition that can look similar. The scales in seborrheic dermatitis are thinner, have a yellowish tint, and feel oily or greasy. In contrast, psoriatic scales are dry, thick, and have the characteristic silvery-white appearance. Seborrheic dermatitis tends to be confined to areas rich in oil glands, whereas psoriasis often extends beyond the hairline.
Scalp eczema, or atopic dermatitis, is another condition that causes flaking and itching but presents differently from psoriasis. Eczema patches are less sharply defined, having fuzzy or indistinct borders. Unlike the dry plaques of psoriasis, severe eczema can present with weeping or crusted skin, a feature rarely seen in uncomplicated psoriasis.