Claudins are major components of tight junction complexes that regulate epithelial permeability. Claudin 1 (CLDN1), a member of the Claudin family, is a key membrane protein in tight junctions. CLDN1 is essential for preventing the paracellular diffusion of small molecules through tight junctions in the epidermis, maintaining the skin's normal barrier function. Loss-of-function mutations in CLDN1 result in neonatal ichthyosis-sclerosing cholangitis syndrome. Studies have shown that CLDN1 plays a regulatory role in cancer and may serve as a potential therapeutic target. Additionally, evidence indicates that Claudins are important in tumor immunotherapy and have significant therapeutic potential. The Claudin 1 protein product may enhance the development of drug discovery efforts related to its therapeutic potential.