The fact that in some individuals the ingestion of certain articles of diet, perhaps notably fruits, is followed by marked skin eruptions - erythema or urticaria (nettle-rash) - shows that there is an important relationship between the processes of digestion and the skin. The eruptions referred to are undoubtedly of a toxic nature, and represent the attempt of the skin to excrete a poison circulating in the blood, this poison having been absorbed from the alimentary canal. The subjects of diabetes are specially prone to skin eruptions, notably of the nature of boils; and since diabetes is essentially a disorder of nutrition, we have here further evidence of the close relationship that exists between diet and derangements of the skin functions.

Speaking generally, it can be stated that there is no evidence that diet enters largely into the treatment of most skin disorders. There are, however, some skin diseases in which the food factor is an important one. These are seen both in children and in adults, and may be shortly referred to.

In Children

Children, and more especially the children of gouty parents, by no means infrequently develop skin eruptions that are dependent on faulty feeding. The most common forms of eruptions are small and large reddish spots of an erythematous nature, and more or less defined areas of nettle-rash (urticaria). These eruptions are usually the result of absorption of some toxin absorbed from the bowel, this toxin being produced under one or other of the following conditions: -

1. The use of too stimulating food, and more especially an excessive supply of meat foods.

2. Over-indulgence in sweets, usually in the form of confectionery or fruits.

3. The food being over-abundant, and too rich and varied.

More rarely the eruptions occur in children who are being too exclusively fed on a diet rich in carbohydrates and fats which has laid too great a strain on the liver. In every case we must first seek to determine the cause, and an examination of the stools in children is a valuable aid in determining this; and having ascertained in which direction the diet was defective, the fault must be corrected. Frequently a little mild starvation for twenty-four to forty-eight hours is advantageous. Castor oil, a little magnesia, and a few doses of grey powder are helpful factors in treatment. The subsequent use of a more physiological dietary will prevent the repetition of the skin trouble.

In Adults

Eczema, psoriasis, urticaria, acne, and pruritus are skin diseases seen in adults which can not infrequently be very beneficially treated by diet. Eczema, psoriasis, and urticaria are most frequently seen in gouty individuals; acne is sometimes dependent on excessive indulgence in alcohol; pruritus is met with in diabetic subjects and in cases with pentosuria (p. 377). The dietetic treatment of the skin condition is, therefore, the dietetic treatment of the underlying disease, gout, diabetes, etc.

Most commonly the error of diet has been in the direction of excess - excess of meat, excess of sugar, or excess of alcohol in various forms. These cases are, as a rule, best treated by a lacto-vegetarian diet, in which in addition the amount of sugar is restricted, and all alcoholic liquors forbidden, the aim of dietetic treatment being to diminish the auto-intoxication that is the causal factor in the disease. As in children, calomel and salts are important adjuncts in treatment.