This section of the book is from "The Complete Herbalist" by Dr. O. Phelps Brown. Also available from Amazon: The Complete Herbalist: The People Their Own Physicians By The Use Of Nature's Remedies.
This annoying disease is caused by minute white insects, the acarus scabei or sareoptis hominis, which insinuate themselves beneath the skin. It is said that these insects travel in pairs, male and female, husband and wife evidently, and that the female is very much the smaller. Under the microscope the animal appears in the cut, which gives a front, back and side view of it. The elegance of the animal is beyond question, and his mode of burrowing under the skin is sagacious. When placed upon the skin he proceeds to make a hole through it, which he does by his head and fore-feet. Into this he insinuates his whole body. Like the mole, he makes a channel many times his own length, at the end excavating a chamber, where he takes his siesta, and from whence he saunters forth in quest of provender. As age approaches, tired of the home of his youth, he digs onward, scoops out another in which he ends his days, beloved and respected by all his neighbors.
Itch is characterized by a vesicular eruption, and makes its appearance between the fingers and in other soft portions of the skin. If the pimples are scratched a watery fluid is poured out which forms small scabs, and if the disease is not cured, extensive sores occur. It is more common among the poor, but James I. of England said that it was only fitted for kings, so excellent is the enjoyment of scratching. It may be a royal luxury, but I am quite sure that persons having the itch would consent for it to be entirely monopolized by kings. A similar disease is caused by the acarus sacchari, an insect very common in brown sugar.
TREATMENT. -- Whatever kills the little animal will cure the itch. This is best achieved by sulphur. It should be made into an ointment with lard, and thoroughly rubbed into the skin before the fire, morning and evening for a few days. This will put an end to the "squatter sovereignty" of whole colonies. An ointment made from veratrum also does well. Another method is equally if not more efficacious. Rub the entire surface of the body over with soft soap for half an hour -- then a warm bath for half an hour, washing it thoroughly off, and exciting the skin to active circulation. Then an ointment, prepared as follows, should be rubbed over the entire surface: Take eight ounces of lard and into it thoroughly rub two ounces of flour of sulphur, and one ounce of carbonate of potash, making an even and uniform mixture, and it is ready for use. This, after it has remained on the skin for three hours, may be well washed off, and the disease is entirely annihilated. In persons of tender skin, or where considerable inflammation has been set up by continued scratching, it may be necessary to anoint with hard soap instead of soft, for it does not contain as much alkali, and leave out the carbonate of potash in the ointment -- for reason of its being too stimulating. In these instances, it will take longer to cure the disease, but it is just as certain in its results. This mode of treating this disease is an entirely successful one -- and no one need "to scratch" if these simple directions be attended to.