Pepppermint essential oil has been proven effective for headache relief and digestive disorders. Read the full report at: Medscape Medical News. It is critical that you buy essential oils from a reputable source. The sole ingredient(s) in an essential oil should be plant-based. Chemical additives decrease the effectiveness and introduce unwanted contaminants to the body. Many oils available today are not plant essences but instead are merely chemical replications which have absolutely no therapeutic benefits.