Thymol (also known as 2-isopropyl- 5-methylphenol, IPMP) is a natural monoterpene phenol derivative of cymene, C10H14O, isomeric with carvacrol, found in oil of thyme, and extracted from Thymus vulgaris (common thyme) and various other kinds of plants as a white crystalline substance of a pleasant aromatic odor and strong antiseptic properties.
Thymol has microbial activity because of its phenolic structure, and has shown antibacterial activity against bacterial including Aeromonas hydrophila and Staphylococcus aureus.
Thymol has been used in alcohol solutions and in dusting powders for the treatment of tinea or ringworm infections, and was used in the Unites States to treat hookworm infections. It is also used as a preservative in halothane, an anaesthetic, and as an antiseptic in mouthwash. When used to reduce plaque and gingivitis, thymol has been found to be more effective when used in combination with chlorhexidine than when used purely by itself.
Thymol is also the active antiseptic ingredient in some toothpastes, such as Euthymol. A minor use of thymol is in book and paper conservation. Paper with mold damage can be sealed in bags with thymol crystals to kill fungal spores. However, this practice is not currently recommended due to apparent accelerated degradation suffered by these objects.