Wintergreen (Gaultheria procumbens) essential oil is extracted from the leaves of a small evergreen herb that grows up to 8 inches tall. The crushed leaves have a lovely medicinal smell. It is often blended to a 10% concentration in the carrier oil of your choice, and used as an effective pain-relieving massage oil. The essential oil of Wintergreen, being made up almost exclusively of methyl salicylate, a precursor to common aspirin; Wintergreen should NOT be used by people who are allergic to aspirin. Further, Wintergreen should NEVER be ingested, and only used topically in dilutions of 25% or less. This pale yellow oil with an intense sweet-woody aroma should be diluted significantly before topical application - it would be a fine addition to any formulas for supporting joint and muscular aches and pains. Care must be taken to use Wintergreen in modest amounts, and to always keep the oil away from children. One should consider it a bottle of liquid aspirin in this regard. Always test a small amount of essential oil first for sensitivity or allergic reaction, dilute properly. If pregnant or under a doctor's care, consult a physician.