Xerosis, or dehydration of skin is also a likely cause. Ichthyosis and xerosis have been relieved by the topical use glycerin. Humectants have been added to skin moisturizing products to treat xerosis. Urea 40% is indicated for psoriasis, xerosis, onychomycosis, ichthyosis, eczema, keratosis, keratoderma, corns, and calluses. In vitamin A deficiency, mucus-secreting cells are replaced by keratin-producing cells, leading to xerosis.