Wintergreen on commercial market may actually be from Betula lenta or Gaultheria shallon. Oil of Wintergreen has been available in synthetic form for quite some time. This synthetic oil is used as a flavoring agent and in medical preparations. Think toothpaste and drug store muscle rubs. Wintergreen essential oil contains up to 90% methyl salicylate, essentially the active ingredient. Wintergreen is mildly analgesic and is an expectorant. This oil acts as an anti-inflammatory and is a rubefacient ( reddens the skin) It is used mainly in massage when addressing sore muscles and arthritis pain. Wintergreen is stimulating to the liver and can ease headaches that are liver related. Use this oil well diluted because it can be irritating and is absorbed rapidly. Ingestion is toxic. As an aside, it can be argued that Wintergreen is not an essential oil because the oil does not occur naturally in the living plant, rather it is produced by an enzymatic reaction during the extraction process.