A poultice is a soft, moist mass that is spread on cloth and applied to the skin to treat various ailments such as insect bites, arthritis, and infections. It is made by mashing herbs, plants, or other substances with warm oil into a paste. Common types include onion, potato, mustard, and comfrey poultices. Poultices are also used to remove stains from stones by using a porous material filled with a solvent like ammonia or alcohol. They are a common treatment for horses to relieve inflammation.