DIY Pain-Relieving Salve with Essential Oils. Wintergreen and birch essential oils are wonderful but extremely potent and should be handled with care. Birch and wintergreen are nature’s painkillers, which is why they are perfect for a pain-relieving salve. Be sure to only use pure, therapeutic essential oils! Use this salve for joint pain, rheumatism, sore muscles, arthritis, headaches, inflammation, cramps, sprains, frozen shoulder, tendonitis, and other pain.