A volatile liquid of penetrating odor, found in nature in the wintergreen, Gaultheria procumbens, called the teaberry, and in the sweetbirch, Betula lenta. It is composed chiefly of methyl salicylate, and this is the official form in which these oils are listed. Methyl salicylate, besides being distilled from the plants, may also be made artificially, and its label must now indicate its natural or synthetic character. The artificial oil is now largely used instead of the natural oil.

The physiological actions of the oil of gaultheria are the same as those of salicylic acid.

It is given in emulsion or capsules.

Average dose,  x.-0.65 mils.