It is not known when it was first used as a condiment, but the Roman were known to have blended the crushed mustard seeds with must to make a sauce. For centuries, mustard was considered everyone's favorite cure-all. The Romans introduced it to Britain, and by the tenth century it had become an important medicinal plant. At that time it was a popular head-ache remedy. Bronchial congestion was also relieved by a combination of mustard, vinegar, water, and honey.
Black mustard contains two chemicals compounds, myrosin and sinigrin.
They are responsible for the strong odor. They react with each other in the presence of water to form a volatile oil of mustard. One drop of this oil can cause severe blistering. However, when carefully controlled, this oil had important medicinal uses. Volatile oil mustard used to be an ingredient that, when taken internally, was reported highly successful in promoting the absorption of scar tissue.