Urticaria is the result of a special kind of reaction of the skin in which the vaso-motor nerve system is specially involved, and may be excited by external or internal irritants, directly as in a nettle sting, or reflexly in some visceral irritation (stomach and genital organs). It is well known that some poisons, e.g. that formed in certain mussels, may be powerful enough to induce the vaso-motor trouble in any one ingesting the food. There are persons also who, temporarily or persistently, have an idiosyncrasy against certain articles of diet, or whose digestive power is, at any rate for a time, imperfect for such food, and in them this special reaction is excited, though such articles of diet are innocuous to the general run of people. Toxins formed in the intestines are also incriminated. On the other hand, the cutaneous vaso-motor nerve system seems to be in a very unstable condition, and then the slightest stimuli produce the wheals. A striking example of this is seen in autographism; and in the effects of undressing or getting warm in bed in certain subjects. Of late years the state of the blood has been investigated in cases of urticaria, and in some instances found deficient in coagulation power, readily allowing "serous haemorrhages." Alcoholism has a special tendency to impair the tone of the vaso-motor nerves, and also acts by causing gastro-intestinal and liver troubles. From these remarks the lesson will be learnt that in urticaria we must thoroughly investigate the state of the nervous system, inherited or acquired, and look carefully for an exciting cause in the food intake and digestion, and examine the urine for evidences of imperfect elimination, and correct what is wrong by insisting on a diet simple in quantity and quality. In some distressing chronic cases it will be found expedient to experiment for a time with a special dietary, as milk, lacto-vegetarian, etc.