Irritant thyme

Essential oils high in phenols that are skin irritants include cinnamon, clove, aniseed oil, basil, tarragon, red thyme and origanum. 

Thyme oil contains thymol and carvacrol (phenols p. 59), which are also dermal irritants, but with linalool and other noncyclic alcohols the risks are significantly reduced. 

Essential oils that may cause irritation of mucous membranes include fennel, pine, spruce, clove, oregano and thyme. 

PROP Main constituents are thymol, carvacrol. Found in plants Thymus vulgaris L. and Thymus sygisL. (FCTXAV 12,807,74). SYN SPANISH THYME OIL SAFETY PROFILE MHdly toxic by ingestion. A severe skin irritant. When heated to decomposition it emits acrid smoke and irritating fumes. 

Composed of complex organic compounds (phenols, acids, alcohols, ethers, ketones, and aldehydes), volatile oils evaporate when exposed to air. Volatile oils are found in many plants and may produce the aroma of the plant. Volatile oils exhibit various properties but some common oils are antiseptic or local irritants, or sedative. Oils of peppermint, clove, cinnamon, garlic, and thyme are volatile oils. 

Thymol (thymic acid) is extracted from essence of thyme. It is four times more bactericidal than phenol and ten times less toxic. Thymol iodide is used on burns in the same way as iodoform, but has the advantage of not being absorbed and not having any odor. It is less irritating on wounds and mucous membranes than dithymol diiodide or aristol. Thymol iodide powder, an antiseptic that is used often after a phenol peel, physically alters the selective permeability of plasma membranes. It is nevertheless a protoplasmic poison that denatures enzyme proteins and is also an allergen. 

While present in only a relatively few aromatic herbs, phenolic volatile oils are among the most potent and potentially irritant compounds found in essential oils. Phenols are represented in both major classes of aromatic compounds—the monoterpenes and phenylpropanoids. The major monoterpene phenols, thymol and carvacrol, are found in thyme. Thymus spp., and oregano. Origanum vulgare (Lamiaceae). 

Thyme oil consists entirely of terpenes, the most dominant being a mixture of the phenols thymol and carvacrol. Other compounds present are the alcohols linalool, geraniol and a-terpineol (Stahl-Biskup 1991). Thymol is an expectorant, antimicrobial, anthelminthic and antispasmodic. It is a dermal and mucous membrane irritant and caution is required in its use. The tincture is a safer means of administration than the oil itself. 

Thymol and carvacrol, usually the major phenols present in oregano, have strong fungicidal, anthelmintic, irritant, and other properties (see thyme). 

Red thyme oil has been reported to be nonirritating, nonsensitizing, and nonphototoxic to human skin but severely irritating to mouse and rabbit skin when applied undiluted. ... 

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