They are usually oils and work if applied after a bath. They fill the spaces between dry flakes with droplets of oil. Used alone they provide only temporary relief. Keratolytic agents cause cellular damage of the cells in the stratum corneum with the result of cell shedding. Keratoplastic agents cause a normalization of the epidermal cell kinetics by having a cytostatic effect on the basal layer and therefore, slowing down epidermal proliferation.
Most agents used in veterinary dermatology for the treatment of seborrhea have both properties.
Tar is keratolytic, keratoplastic, antipruritic, degreasing, and drying. It may be irritating and may cause photosensitivity. It may stain a white hair coat. Tar is contraindicated in cats . Synergism with salicylic acid is proposed.