This review article explores the potential applications of chitosan, a natural polysaccharide derived from crustacean shells, in the treatment of seborrheic dermatitis (SD) and other skin diseases. SD is a common chronic inflammatory skin condition characterized by erythema, scaling, itching, and an oily appearance, predominantly affecting areas rich in sebaceous glands. Current treatments, including antifungal agents, corticosteroids, and calcineurin inhibitors, offer symptomatic relief but have limitations in long-term use due to side effects and resistance issues. Chitosan exhibits excellent biocompatibility, biodegradability, and broad-spectrum antibacterial properties, making it a promising candidate for SD treatment. This review highlights chitosan's multifunctional properties such as antimicrobial, anti-inflammatory, sebum-regulating, and barrier-enhancing effects, which are closely related to the pathogenesis of SD. Additionally, the article summarizes the applications of chitosan in other skin conditions, including wound healing, infectious skin diseases, and atopic dermatitis, demonstrating its broad therapeutic potential. Through this comprehensive evaluation, the review aims to provide a theoretical foundation for clinical research on chitosan in SD and support the development of new, safer, and more effective treatment options for various skin conditions.