" A phenol occurring in the volatile oils of Thymus vulgaris, Linné, Monarda punctata, Linné (Nat. Ord. Labiatae)," etc.

Large, colorless, translucent crystals of the hexagonal system, having an aromatic, thyme-like odor and a pungent aromatic taste, with a very slight caustic effect upon the lips. Soluble in about 1,200 parts of water at 59° Fahr. (15° C), and in less than its own weight of alcohol; also readily soluble in carbon disulphide, glacial acetic acid, and in fixed and volatile oils. When triturated with about equal quantities of camphor, menthol, or chloral, it liquefies. (U. S. Ph.)

Physiological Actions

The composition of this group of oils indicates the close correspondence between them and carbolic, salicylic, and benzoic acids. So intimate are the chemical relations of salicylic acid, benzoic and cinnamic acids, that the balsams might with propriety be grouped with the antiseptics, for in their physiological actions and therapeutical applications they are equally as closely related as in their elementary composition.

Of the members of this group, thymol or thymic acid has been most elaborately studied. Lewin has shown that thymol, as respects its influence on fermentation and putrefaction, has a positive antiseptic property. Its actions are similar to those acids of the same class to which it is so closely allied chemically, viz., carbolic, salicylic, and benzoic. Locally applied, thymol, just as carbolic acid, produces paralysis of the end-organs of the sensory nerves (Lewin).

The effects of thymol have also been studied by Baltz. He has ascertained that from twenty to thirty grains a day are necessary to produce distinct effects. Placed in contact with the fauces, it causes an acrid sensation, which persists. It rarely excites vomiting, but a large dose induces a sensation of heat about the epigastrium, and sometimes diarrhoea. In the majority of cases thymol causes, in about half an hour to an hour, sweating more or less profuse, but distinctly less than that produced by salicylic acid and jaborandi. The urinary secretion is sometimes increased. The urine presents a dark, greenish hue, as if it contained blood. This is due to the presence of a decomposition product of thymic acid, and in part of thymol itself, for a portion of that taken escapes unchanged (Blum). Singing in the ears, deafness, constriction of the forehead, are caused by full medicinal doses, and a considerable decline of febrile temperature takes place. Decided sweating is coincident with the fall in temperature, and a rigor usually succeeds. It may cause coma, and ordinary apyretic doses have induced great weakness and cardiac failure. Toxic doses in animals cause death by failure of respiration. It is an antiseptic, and is destructive of pathogenic organisms. It is also analgesic, and lessens the sensibility of the sensory nerves.

Thymol, therapeutically, is employed as an antiseptic and antipyretic. It is used as a mouth-wash in dental practice to allay the sensibility of the mucous membrane, when the gums are spongy, to arrest retraction of the gums, as a gargle in faucial troubles. For this purpose a solution varying in strength from 1 to 10 parts in 1,000, or as an ointment in from 1 to 5 per cent, may be employed.

In gastric and intestinal catarrh, thymol acts well to arrest fermentation and stimulate digestion. As an anthelmintic, it has acted favorably, but large doses—from 10 to 30 grains—are necessary to dislodge ascarides. It is said to destroy anchylostoma, and to prevent or remove the secondary troubles caused by this parasite. For this purpose the dose should be one or two grains several times a day.

As an antipyretic, thymol has been employed in fevers, in pneumonia, and in inflammatory affections. The large doses—from 10 to 30 grains—required to effect any considerable reduction of temperature, the sweats, chills, and depression of the powers of life which are thereby caused, render its use doubtful, even prohibitory. As thymol exercises a deterrent influence over the microbes of phthisis and diphtheria, it has been used topically with a certain measure of success. To this end it is used in the form of spray and by inhalation, of the strength of 1 per cent.

Externally, thymol is used in the treatment of parasitic skin diseases, as tinea and pityriasis versicolor, with success. An ointment of 5 per cent in lanoline or vaseline is suitable for this purpose.