Not to discredit dear old Grandma, but she didn't come up with the mustard plaster, although by the way she touts its virtues, you might believe so. Actually, this ancient remedy for the flu, chest colds, and bronchitis dates back to the Ancient Romans, who early on understood the healing properties of mustard. Mustard is loaded with antimicrobial and anti-inflammatory properties, many of which can be inhaled through the vapors. Impress Grandma by making a mustard plaster with 1 tablespoon dry mustard and 2 to 4 tablespoons flour. Mix both with 1 egg white (optional) and warm water to form a paste. Next, find a clean handkerchief or square of muslin large enough to cover the upper chest. Smear the cloth the same way you'd smear mustard on a sandwich, then plop another cloth over it. Dab olive oil on the patient's skin and apply the mustard plaster to the upper chest. Check yourself or the patient every few minutes since mustard plaster can burn. Remove after a few minutes. Afterward, wash off any traces of mustard from the skin.