Sulphur is one of the substances which are fatal to acari, and it still remains one of the best, as it is the commonest, remedy for scabies, though Dr. McCall Anderson and others have objected to it as too irritant.

It is nearly certain that sulphur, when used by itself or mixed with lard, has simply a mechanical effect on the epidermis; but when carbonate of potash is added to the ointment, sulphurated potash is formed, and this compound quickly destroys the acari. We know, from clinical observation, that these insects often live in the plain sulphur ointment for several days without much apparent detriment, while, as Kuchenmeister says, "the acari, kept in a solution of sulphurated potash, die in a quarter of an hour."

The strength and the frequency of the application should be varied according to the delicacy of the patient's skin and the amount of the eruption; the more active the preparation, and the more thorough its use, the quicker will be the cure. Thus, painting the body with a solution of chloride of sulphur in sulphuret of carbon is said to cure in five minutes (Medical Times, i., 1856, pp. 247, 368); while Bourguignon's formula with lime and sulphur (boiled together) is allowed half an hour, and M. Hardy's method with soft-soap frictions, warm bath, and anointing with 2 parts of sulphur to 8 of lard and 1 of potash carbonate, effects its purpose in four hours (British and Foreign Review, ii., 1852, Lecons); but such results are liable to be accompanied with unnecessary irritation and pain to the patient. Dr. Tilbury Fox, having seen eczematous eruptions and chronic irritation often induced by the excessive use of too strong an ointment, and founding his advice on observation of the parts usually affected, advocates the use of a mild ointment (1 part in 16, i.e., 1/2 dr. to the ounce of lard) to the wrists and between the fingers only, in acute cases accompanied with general irritation (Lancet, ii., 1871); but, as Hebra and R. Liveing observe, the restriction of the application to a few portions needs very exact diagnosis, and, as a rule, the ointment of the selected strength should be applied to every part. A prolonged warm bath (half-hour), and thorough cleansing with soap and friction, should precede the inunction; then, after drying, either the mild ointment of Fox, or the simple ointment of the Pharmacopoeia (1 part in 5), or one of intermediate strength (1 part in 8, with 1/2 a part of potash carbonate) should be plentifully rubbed over the trunk and the limbs, especially the flexor side of the limbs and between the fingers and toes; and then socks, gloves, drawers, and jersey should be used to keep the ointment in contact with the skin (Liveing). An ointment I commonly prescribe is made with sublimed sulphur, 2 dr.; sulphide of calcium, 1/2 dr.; and simple ointment, 2 oz. After a night's application, a warm bath in the morning may be used to remove the odor of sulphur, but then a second or third inunction may be required; if the first one can be left undisturbed for twenty-four hours, it will often suffice to cure. In some cases, a lotion of sulphuret of calcium (liquor calcis c. sulphure) acts better, because it is more thoroughly applied than an ointment; its use should also be preceded by a warm bath, and it need only be gently applied with a sponge or brush; if used with friction it may cause very severe irritation.

A sulphur-bath is not so effacious as these remedies, but may sometimes be required, and may be made with half a pound of sulphurated potash to thirty gallons of water - or with sulphur, hyposulphite of soda, and acid (v. Preparations). Wooden or porcelain vessels should be used for the baths, of which several will be required. Sulphur in vapor may also be employed.

It is important to remember that irritation of skin may remain even after the scabies itself is cured, and this irritation is to be treated by soothing remedies; sulphur is not to be continued longer than absolutely necessary for the destruction of the parasite. Sometimes it may be altogether contraindicated, or may be inconvenient, and then recourse may be had to styrax, tolu, petroleum, or iodide of potassium; but in most cases the preceding method will give satisfactory results.