Peppermint Worst Fragrance Synthetic and Natural No known benefits Peppermint description Both the oil and the extract form of peppermint can have beneficial properties, but they can also have a sensitising effect on skin. Peppermint oil is a more potent sensitizer than peppermint water. Peppermint is a common cause of sensitivity on the face, particularly around the mouth, as it’s frequently used as flavoring in toothpastes. The oil contains 44% menthol, an ingredient believed to be largely responsible for peppermint oil’s benefits as well as its risks. Related ingredients: Menthol