Mustard plasters are still being used today to treat rheumatism, arthritis, chest congestion, aching back, and sore muscles. To make a mustard plaster, mix equal parts powered mustard and wheat flour, dilute the mixture with sufficient cold water to achieve a soft paste. Spread on a clean cloth such as cotton flannel, linen, or several layers of muslin. Remember that mustard is a hot herb and contact with the skin may cause blistering and should be avoided. Leave on for approximately 15 minutes. If the patient complains at any time during treatment, remove the plaster immediately. After the plaster is removed, bathe the treated area with cool (not cold) water to stop the burn. Dry the area and finish up with a dusting of baby powder or cornstarch to soothe the skin