Scalp Itch: A Systematic Review

The 2017 document reviewed scalp itch and proposed a classification system based on the presence of dermatological lesions and hair loss. It introduced the SCALLP acronym for common causes: seborrheic dermatitis, contact dermatitis, anxiety, lichen planopilaris, lice, and psoriasis. The review recommended a five-step evaluation process and discussed the pathophysiology, including the role of neuromediators, scalp sebum, and microflora. It noted that seborrheic dermatitis affects about 16% of adults, and psoriasis has an itch prevalence of 67-97%. Contact dermatitis is often related to hair product allergens. The review also covered less common causes and diagnostic tools like trichoscopy. Additionally, it detailed conditions associated with scalp itch, such as sensitive scalp (60% of patients), atopic dermatitis (49.7% with scalp involvement), non-scarring alopecias (alopecia areata, androgenetic alopecia), scarring alopecias (LPP, frontal fibrosing alopecia, discoid lupus erythematosus, central centrifugal cicatricial alopecia), urticarial lesions, infestations, and systemic diseases (dermatomyositis, systemic lupus erythematosus, scleroderma, Sjögren syndrome). Accurate diagnosis and treatment depend on differentiating between these conditions.