DERMATITIS.
Definition.—Inflannuation of the skin.
Varieties.—There are seven varieties of dermatitis: dermatitis traumatica, due to traumatic irritation of the derma; dermatitis venenata, due to contact with poisonous agents; dermatitis medica mentosa; dermatitis herpetiformis; der matitis gangrenosa; dermatitis maligna; and dermatitis exfoliativa.
Dermatitis Traumatica.
Under this heading are included such superficial inflammations of the skin as follow pressure, violence, contusions, abrasions from scratching or rubbing, or the action of mechanical irritants of any kind.
Case of dermatitis from Roentgen rays in a boy aged 16. On October 13th, to radiograph the spine, a Crookes tube was placed about 5 inches from the epigas trimn, a flannelette shirt intervening between the tube and the skin, while the trousers were turned clown on each side. An exposure of one hour was made, the the coil being run by means of an accu mulator. The next day the skin felt irritable and was of a deep-red color in the area subjected to the rays. The irritability increased, and, six days after the experiment, the skin felt stiff when he bent his body. Vesicles began to form, and they increased in size and number. The general surface was of a dusky or purplish red, forming. a,n ir regular band three-quarters of an inch wide round the umbilicug. On October 31st the whole of the epidermis had sep arated, and the skin was quite sound and level with the surrounding skin, except where the vesiculation had been most pi-onounced. The downy hairs with which the abdomen was rather thickly covered were still present on the site of the affected area. H. Radcliffe Crocker (Brit. Med. Jour., Jan. 2, '97).
Case of a man, aged 35 years, on whom an attempt was made to get a Roentgen photograph of the renal region. The exposure lasted one hour. Three hours later he felt nausea. Six days later another attempt was made, this time the exposure being with a somewhat stronger battery for an hour and a half. After
the patient left lie again felt nauseated. Next day the abdomen was slightly red; there was no itching or pain. On the third day redness was more intense. On the fourth day vesicles appeared, ran together, broke, and formed, eight een days after the second exposure, a patch seven and a half by eight and a fourth inches. It looked like an irrita tive eczema, with exfoliated epidermis and a profuse sero-purulent discharge. Sixteen weeks after the second exposure the sore was three by three and a half inches and covered with a thick, leathery, insensitive, false membrane. H. C. Drury (Brit. Med. Jour., Nov. 7, '96).
The inflammation of the skin some times noticed in connection with fluoro scopic or sciagraphic observations is due to the absorption of radiant energy by the cells of the skin, and comparable to the changes effected in the photographic emulsion. Dermatitis appears more likely to ensue from exposure to low than to high vacuum-tube, the vast majority of rays with the former being unquestion ably absorbed by the skin, while with the latter but few are absorbed. Jones (Jour. Amer. Med. Assoc., Nov. 6, '97).
The inflammatory action is usually simple, unless the tissues become in fected by staphylococci or streptococci, when pus-formation or erysipelatous in flammation may follow. A common form of simple dermatitis is that result ing from chafing; while this., under the name intertrigo, is usually classed among the congestive erythemas, it more fre quently runs into true inflammation.
The most frequent sites for the in tertriginous dermatitis are the armpits, perineum, and insides of the thighs and the under-surfaces of pendulous breasts, especially in corpulent women. It is more frequent in summer than in win ter, as free perspiration, macerating the upper layers of the skin, and undergoing decomposition, with the formation of irritant compounds, promotes the oc currence of the inflammation.