<p>Salicylic acid is a widely used and effective keratolytic, it produces desquamation and destruction of the epithelium by solubilising the intercellular cement of the Stratum Corneum. Lactic acid affects the keratinisation process, reducing hyperkeratosis and is also caustic, leading to the destruction of hyperkeratotic tissue. Collodion is derived from cellulose in a base containing ethanol and ether. It allows easy and accurate application of the product and dries to leave a film which hydrates the tissue and facilitates penetration of the active ingredients.</p>