ITCHING DISEASES AND DISEASES DUE TO PARASITES.
Itching (Pruritus) is a condition of per verted sensibility of the skin. It is not to be regarded as a disease in itself, but merely as a symptom of a disease, and it may accompany various disorders. Itching may be present in a very annoying degree without any eruption of the skin at all. But if it is severe, and lasts for any time, the mere mechanical injury in flicted by the nails of the person is likely to produce considerable changes in the appearance of the skin, in the shape of scratches, tender and bleeding spots or patches, from which the protective scarf-skin has been removed, and in flammation and thickening of the affected parts. If the itching attends an eruption the characters of the eruption are considerably altered by the tearing, the tops being scratched off pimples, which are thus made to bleed, and then the blood dries and forms a red crust or cap to the pimple, &c. The itching may be confined to parts of the body or may be spread more or less over the whole body.
1. Itching is very often due to the presence of the itch insect (see THE ITCH), or the louse (see LOUSINESS, p. 432), or to the parasite of ringworm (see RINGWORM, p. 434).
2. It may be caused by the irritation of rough clothing.
3. It may arise because of inflammation of the skin. Thus eczema (p. 425), lichen (p. 427), and sometimes psoriasis (p. 426) and pemphigus (p. 425), are accompanied by itching.
4. It may be due to constitutional and various other diseases. Thus an intense itching about the private parts is often caused by diabetes (p. 407), even in cases where no other symptoms lead to the suspicion of that disease. Itching about the anus is frequently the result of piles. In jaundice the retention of certain biliary con stituents in the blood produces itching of the skin. Irritations of the intestinal canal, caused, for example, by worms, irritative affections of the womb, and affections of the kidney and bladder, may lead to it. In old people changes in the skin, resulting from old age, may cause it.
5. Certain drugs, such as opium and copaiba, after being taken inwardly, tend to produce a general itchiness of the skin.
- Treatment.—As soon as the cause has been found the remedy may be easy. Insects should be destroyed, disease of kidney, womb, &c.,
should be treated, irritation removed if pos sible, and so probably the itching will disappear. ' Where no cause can be discovered, tonics (iron and quinine) should be given ; the person should not wear flannel next his skin, and frequent bathing with water in which ordinary soda is dissolved should be resorted to. A lotion is also recommended consisting of Wright's liquor carbonis detergens, ounce in 8 ounces of water, and 1 ounce of glycerine. With this the parts should be sponged. Soda baths, lysol baths, starch baths, are all useful. After drying, the body should be lightly smeared with menthol oil (30 grains menthol in 6 07.0. olive-oil).
The Itch (Seabiea). —This is an itching disease due to the irritation of the itch insect (Acarus scabiei), in which the skin is inflamed (Plate XXV.).
The male itch insect is represented in Fig. 167. It is just large enough to be seen with the naked eye, has eight legs, and a number of projecting spines from its under surface. The female is slightly larger than the male, being about inth to of an inch long, and on the ends of the four front legs it has suckers, while the hind-legs end in long hairs. In the male two of the hind-legs have suckers. When the female is placed on the skin it bores its way into the epidermis, and, after lying embedded for a little, lays an egg. To make room it bores a little farther along, then lays another egg. Daily a fresh egg is laid, the insect meanwhile ad vancing and penetrating into the skin till it has bored a tunnel which passes more deeply into the skin the farther it is carried. With the growth of the skin, and the shedding of the cast off cells of the epidermis, the tunnel is brought nearer to the surface, till the first egg is ex posed, about the time it is hatched. Fourteen clays usually elapse between the laying and hatching of an egg. In one tunnel there are about fifteen eggs. The young insect has at first only six legs, two of the hind-legs being wanting till after it has shed its first skin. The young insects escape from the burrow to the surface of the skin. The females meet males, become impregnated, and pro ceed themselves to burrow. The adult female insect dies at the end of her tunnel.