Fir Needle Oil Dårligst Fragrance Synthetic and Natural No known benefits Fir Needle Oil description Volatile, fragrant oil that can cause skin sensitivity. According to the Natural Medicines Comprehensive Database, “The essential oil also acts as a rubefacient (counterirritant) and improves circulation when applied externally.” A counterirritant is defined as any ingredient that causes sensitisation or a mild swelling of the skin to alleviate uncomfortable symptoms deeper within skin.