Native to the western Mediterranean, Thymus vulgaris (one of approximately 300 Thymus species) is a small bush used for centuries as a spice and in medicine, particularly to treat bronchitis.1Thymus species are among the wild and cultivated species used in traditional medicine in Bosnia and Herzegovina for various indications, including skin disorders.2 Thyme essential oil is a natural compound generally recognized as safe by the Food and Drug Administration, with demonstrated antibacterial, antifungal, and antispasmodic activities.3,4 Several other biologic activities have been associated with the polyphenol-rich herb, many of which have dermatologic implications. Notably, the essential oil of thyme and thymol, a key constituent of thyme, are known to act as skin sensitizers and allergens.5
Dr. Leslie S. Baumann
Photoprotective activity
Recently, Sun et al. showed that UVB-induced skin damage was attenuated by treating hairless mice (HR-1) with T. vulgaris, as indicated by reduced matrix metalloproteinases and elevated collagen synthesis. In cultured normal human dermal fibroblasts, the investigators found that T. vulgaris blocked UVB-induced reactive oxygen species and lactate dehydrogenase, and dose-dependently yielded increases in glutathione, NAD(P)H: quinone oxidoreductase 1, and heme oxygenase-1. Further, the botanical significantly reduced UVB-induced phosphorylation of mitogen-activated protein kinases. The investigators concluded that T. vulgaris has potential for use in preventing skin damage caused by UV radiation–induced oxidative stress.6
Thyme also was demonstrated by Cornaghi et al. in 2016 to exert a protective effect on normal human skin explants obtained from seven young healthy women that were treated 1 hour before UVB irradiation.7
In 2015, Calò et al. evaluated the protective effects of a dry extract from T. vulgaris and its primary synthetic constituent thymol against UVA- and UVB-induced oxidative and genotoxic damage in the keratinocyte cell line NCTC 2544. Both thymol and T. vulgaris suppressed reactive oxygen species production in UVA- and UVB-treated cells, but lowered malondialdehyde synthesis only in cells treated with UVA.8
Antioxidant activity
In 2007, Wei and Shibamoto reported that thyme essential oil mixed with clove oil exhibited over a 90% inhibitory effect against the formation of malondialdehyde. They speculated that the presence of thymol and eugenol might account for the strong antioxidant activity displayed by the thyme/clove leaf combination.9 The investigators previously observed antioxidant activities exhibited by volatile extracts isolated from thyme (as well as various other herbs and spices) using aldehyde/carboxylic acid as well as conjugated diene assays.10 The antioxidant activity of thyme also was demonstrated by Miura et al. using the oil stability index method.11
Antimicrobial activity
In 2011, Sienkiewicz et al. reported that the oil of T. vulgaris displayed potent activity against clinical bacterial strains of Staphylococcus, Enterococcus, Escherichia, and Pseudomonas genera. In addition, thyme essential oil exhibited efficacy against tested antibiotic-resistant strains of bacteria.12 The following year, Sienkiewicz et al. assessed the antimicrobial activity of thyme essential oil against clinical multidrug-resistant strains of Staphylococcus, Enterococcus, Escherichia, and Pseudomonas, finding that it potently suppressed the growth of each.13
Potential cutaneous indications: atopic dermatitis, leishmaniasis, eczema, hair growth
In 2015, Seo and Jeong showed that lavender oil, thyme oil, and a blend of the two were all effective in reducing the symptoms of atopic dermatitis in mice. The researchers suggested that developing treatments with these oils for human patients with atopic dermatitis is warranted.14
Nilforoushzadeh et al. found in 2008 that herbal extracts of T. vulgaris and Achillea millefolium (yarrow), as well as propolis hydroalcoholic extracts, were effective in treating cutaneous leishmaniasis in mice and recommended the study of these extracts alone or in combination in human trials.15
A two-arm, randomized, double-blind, placebo-controlled trial conducted by Shimelis et al. in 2012 evaluated the efficacy of a 3% thyme essential oil antifungal cream and a 10% chamomile extract cream in the treatment of eczemalike lesions. Complete healing was achieved in 10 patients (66.5%) treated with the thyme cream, compared with four patients (28.5%) in the placebo group. Although no significant differences were observed between the active chamomile group and placebo, an appreciable number of subjects improved or healed. The investigators concluded that their findings from this small study suggest that, while more research is needed, a 3% thyme essential oil cream appears to be an inexpensive and readily available option to treat mild to moderate cutaneous conditions, including fungal infections, pityriasis alba, and eczema.16
In 2013, Rastegar et al. found that the combination of herbal extracts (including thyme) and platelet-rich plasma induced significant proliferation of human dermal papilla cells by regulating extracellular signal-regulated kinase (ERK) and Akt (protein kinase B). They concluded that their findings suggest the potential for developing combination therapies intended to improve hair growth.17