The features of the disease are so characteristic that there is, as a rule, no difficulty in distinguishing it from other affections. Erythema simplex, erythema multiforme, erythema nodosum, and erysipelas are to be differentiated. Erythema simplex is a simple hyperæmia, while urticaria is a peculiar inflammatory exudation—a point sufficient to distinguish the two. The papular and tubercular forms of erythema multiforme are to be differentiated by their more persistent character, the locality affected, and the absence usually of marked itching and burning. Erythema nodosum may resemble urticaria tuberosa, but the nodes in the former are usually encountered upon the tibial surfaces, are of much longer duration, and are free from itching. It is only when several wheals coalesce, causing swelling and burning, and then only when occurring about the face, that it may be mistaken for erysipelas; but the evanescent character of the eruption in urticaria, its rapid formation, the itching, and the absence of constitutional symptoms usual in erysipelas, are points of difference.
TREATMENT.—Most cases of acute urticaria may be speedily relieved. Relapses may occur, however, upon repeated exposure to the exciting cause. The prognosis of chronic urticaria, on the other hand, is not always so favorable, and will depend in a great measure upon the ability to remove or modify the predisposing condition. The first essential in the management of a case, therefore, is an investigation into its etiological cause.
In the acute disease, where, as in the majority of cases, gastric disturbance is the exciting factor, a purgative—preferably a saline—should be given. In severe cases, if food is still in the stomach, an emetic will be of service, sulphate of zinc, ipecacuanha, and mustard being the best. The diet should be of the simplest kind. Aperients are generally indicated until recovery takes place. In chronic urticaria, where faulty digestion is the exciting cause, remedies appropriate to that condition are to be prescribed. In all cases attention is to be directed to the state of the general health. If there is a suspicion of malaria, quinine and arsenic may be administered. Functional and organic affections should receive proper management, as they may prove to be the active cause of the disorder. If diuretics are called for, acetate of potassium will often best serve the purpose. The alkaline and laxative natural mineral waters are sometimes useful. In obstinate cases, especially in those in which no assignable cause can be detected, pilocarpine, atropia, tincture of belladonna, chloride of ammonium, bromide of potassium, and arsenic may be tried. Change of climate is at times advisable.
On account of the great distress usually attending the affection, local treatment is demanded in almost all cases. Baths and lotions are the most serviceable methods of applying external remedies. Sponging the surface with vinegar or alcohol, pure or diluted, may afford relief. A lotion of carbolic acid, two to four drachms to the pint of water, will frequently give prompt ease. The latter lotion may be improved by the addition of two or three ounces of alcohol and a small quantity (one to two drachms) of glycerin to the pint. A lotion of thymol, one grain to the ounce of alcohol and water, is likewise of value. Benzoic acid and borax, each five to ten grains to the ounce of water; chloral, ten to twenty grains to the ounce; dilute hydrocyanic acid, one to three drachms to the pint; and diluted ammonia-water,—may also be mentioned. Alkaline baths made with carbonate of sodium or potassium, three or six ounces to the bath, are sometimes serviceable. Starch, gelatin, and bran baths may in like manner be used; and acid baths, half an ounce of hydrochloric or nitric acid to the bath, have been recommended. Dusting-powders, especially when applied after baths, will in some cases prove acceptable.
URTICARIA PIGMENTOSA, called also zanthelasmoidea, is an unusual form of the disease, cases of which during the past few years have been reported. It begins usually in infancy, and may continue for a period of months or years. The wheals are intensely itchy, are more or less persistent, and leave yellowish, orange-colored, greenish, or brownish stains. Its nature is obscure: by some observers it is regarded as an urticaria; by others it is claimed that there is a new-growth element in the lesions. Most cases certainly show urticarial lesions and run the course of this affection. It is more than probable that the different cases reported are not examples of one disease. Treatment is, as a rule, unsatisfactory.
Dermatitis.
Dermatitis, although in its general meaning signifying any inflammation of the skin from whatever cause or character, is a term usually applied to those forms which are directly traceable to the action of irritants. Such irritants may act from without, as cold, heat, caustics, etc., or through the medium of the blood, as in the eruptions following the ingestion of certain drugs. The intensity of the inflammation varies from a simple erythematous condition to actual gangrene. Redness, heat, pain, swelling, and at times itching, the common clinical signs of inflammation, are present, but are variable as to degree. The inflammation may be confined to a small area or may be diffused, depending usually upon the cause. The forms of dermatitis are designated according to the causes which produce them.
DERMATITIS TRAUMATICA.—Under this head are included all those inflammations of the skin which are due to traumatism. Contusions and similar injuries, abrasions and inflammation from the pressure of tight-fitting garments, bandages, etc., excoriations, and the like, are common examples of this form. The excoriations from scratching in pediculosis, scabies, pruritus, eczema, and other itchy diseases are to the dermatologist the most frequent examples of traumatic dermatitis. They subside on removal of the cause, leaving often, especially if the scratching has been at all violent and the cause long continued, thickening of the skin and pigmentation, both of which, notably the latter, may be more or less permanent.
DERMATITIS VENENATA.—All inflammatory conditions of the skin due to contact with deleterious substances are classified in this group. Apart from chemical irritants, certain plants, notably those of the rhus family, are capable in some individuals of producing inflammation of the skin. The two well-known plants of this group are the poison ivy or oak and the poison sumach or dogwood. The majority of persons are not affected by these plants, but in many contact, or in some mere proximity to the plant, will be followed by a dermatitis, variable as to degree. The inflammation may simply be of an erythematous character with slight swelling, or, on the other hand, it may be vesicular, pustular, or bullous, with marked hyperæmia, oedema, and swelling. As a rule, the inflammation appears soon after exposure or contact, sometimes within a few hours; not infrequently, however, several days will elapse before the symptoms present themselves. Itching is commonly a prominent symptom, as also heat and burning.
The eruption usually begins as an erythema with heat, swelling, oedema, and itching, remaining for several days, and then subsiding, or, as is frequently the case, vesicles or even blebs are developed, and the affection then is, as a rule, slower in disappearing. Oedema and swelling may be slight, or, as often occurs, so great as to cause marked temporary disfigurement. The face, hands, and genitalia are the parts generally involved, although the disease may extend to other regions, at times involving large areas or even the greater portion of the whole surface. The lesions, either spontaneously or through violence, rupture, and dry to crusts, and subsequently fall off, leaving erythematous spots, which in turn gradually fade. The affection runs an acute course, lasting from one to six weeks. In some cases, especially in those with a tendency to eczema, its duration may be prolonged. The poisonous principle has been found to be toxicodendric acid, and is exceedingly volatile in character.