Salicylic acid is an organic acid found in willow bark and is most widely known as the precursor to acetyl salicylic acid, otherwise known as Aspirin.

Salicylic acid is keratolytic, promoting the removal of epidermis and so has been found to be very effective for treating digital dermatitis, particularly the proliferative (hairy) and hyperkeratotic (warty) stages. The low pH may also make it bacteriocidal, particularly as the spirochaetes causing digital dermatitis are largely unviable at below pH 5