Psoriasis is a chronic inflammatory condition driven by an overactive immune system, which mistakenly signals skin cells to grow at an accelerated rate. Normally, skin cells take about a month to mature and shed, but in people with psoriasis, this process is dramatically shortened to just a few days. This rapid cell turnover leads to the characteristic buildup of skin, which can occur anywhere on the body. When this affects the skin of the head, it is known as scalp psoriasis.
The Appearance of Psoriasis Plaques
The primary physical manifestation of scalp psoriasis is the formation of thick, raised lesions known as plaques. These patches have distinct, well-defined borders and result from skin cells accumulating faster than the body can shed them.
The color of the underlying plaque can vary significantly depending on skin tone and the level of inflammation. On lighter skin, the patches often appear pink or red, while on darker skin, they may present as darker red, purple, or brown.
Overlying these raised, inflamed patches is the most recognizable feature: a heavy layer of scale. This scale is typically dry, powdery, and has a characteristic silvery-white or gray sheen. The texture is thick, often feeling rough or crusted to the touch.
The scales may adhere tightly to the scalp and hair shaft, sometimes building up into a thick, matted layer. This buildup can occasionally resemble overlapping tiles, making the plaques noticeable. While the scales can flake off, mimicking severe dandruff, the underlying patches remain raised and firm.
Associated Symptoms and Affected Areas
Beyond the physical appearance of the plaque, scalp psoriasis is commonly accompanied by uncomfortable physical sensations. Intense itching, medically known as pruritus, is the most frequently reported symptom. This sensation can range from mild annoyance to an overwhelming urge to scratch.
The plaques can also cause a burning sensation, soreness, or tenderness, especially when the scalp is rubbed or washed. Aggressive scratching can lead to the removal of scales, causing the underlying skin to crack and potentially bleed.
Scalp psoriasis can affect the entire head, but it frequently appears in specific locations. It often extends past the hairline, showing up prominently on the forehead, the back of the neck, and around the ears. When it involves the perimeter of the head, it is often referred to as the “crown of the head” distribution.
In instances of severe inflammation or excessive scratching, individuals may experience temporary hair shedding or thinning in the affected areas. Scalp psoriasis does not typically cause permanent hair loss; hair growth usually resumes once the inflammation is managed and the skin has healed.
How Scalp Psoriasis Differs from Dandruff
Distinguishing scalp psoriasis from other common scalp conditions, particularly dandruff and seborrheic dermatitis, is a frequent challenge. The most significant point of difference lies in the morphology of the scales themselves. Psoriasis scales are thick, dry, and possess the distinctive silvery color and powdery texture.
Conversely, flakes associated with common dandruff or seborrheic dermatitis are finer, thinner, and often appear yellowish or slightly greasy. The underlying skin in seborrheic dermatitis is less inflamed than the distinct, highly raised, and firm patches seen in psoriasis.
The location and border definition of the lesions also provide clear differentiating clues. Psoriasis lesions have sharply defined borders and often extend beyond the hair-bearing scalp onto the surrounding skin of the forehead and neck. Seborrheic dermatitis tends to remain localized within the confines of the scalp.
In summary, while both conditions produce flaking, the hallmark of scalp psoriasis is the presence of thick, silvery, raised plaques with defined edges, which contrast sharply with the finer, yellowish, and sometimes oily scales of seborrheic dermatitis.