sed collection of
semi-fluid material in the upper layers of the skin. The vasomotor
nervous system is probably the main factor in its production; dilatation
following spasm of the vessels results in effusion, and in consequence,
the overfilled vessels of the central portion are emptied by pressure of
the exudation and the central paleness results, while the pressed-back
blood gives rise to the bright red periphery.

#From what diseases is urticaria to be differentiated?#

From erythema simplex, erythema multiforme, erythema nodosum, and
erysipelas.

#Mention the diagnostic points of urticaria.#

The acuteness, character of the lesions, their evanescent nature, the
irregular or general distribution, and the intense itching.

#What is the prognosis in urticaria?#

The acute disease is usually of short duration, disappearing
spontaneously or as the result of treatment, in several hours or days;
it may recur upon exposure to the exciting cause. The prognosis of
chronic urticaria is to be guarded, and will depend upon the ability to
discover and remove or modify the predisposing condition.

#What systemic measures are to be prescribed in acute urticaria?#

Removal of the etiological factor is of first importance. This will be
found in most cases to be gastric disturbance from the ingestion of
improper or indigestible food, and in such cases a saline purgative is
to be given, probably the best for this purpose being the laxative
antacid, magnesia; or if the case is severe and food is still in the
stomach, an emetic, such as mustard or ipecac, will act more promptly.
Alkalies, especially sodium salicylate, and intestinal antiseptics are
useful. Calcium chloride in doses of five to twenty grains should be
tried in obstinate cases. The diet should be, for the time, of a simple
character.

#What systemic measures are to be prescribed in chronic and recurrent
urticaria?#

The cause must be sought for and treatment directed toward its removal
or modification. Treatment will, therefore, depend upon indications. In
obscure cases, quinine, sodium salicylate, arsenic, pilocarpine,
_atropia_, potassium bromide, calcium chloride, and ichthyol are to be
variously tried; general galvanization is at times useful, as is also a
change of scene and climate. A proper dietary and the maintenance of
free action of the bowels, preferably, as a rule, with a saline
laxative, is of great importance in these chronic cases.

In