This section is from the "A Handbook of Useful Drugs" book, by State Medical Examining and Licensing Boards.
Poultices are soft solid preparations used for the purpose of applying heat and moisture to localized areas of the body. This application of heat induces a superficial hyperemia which is believed to influence the circulation of underlying parts. The poultices may also be made the means of applying counterirritant drugs. A long-continued application tends to cause relaxation of the skin and to render it flabby.