Acne, which is very common for a few years after puberty, shows a bad condition of the blood. Even during the changes that occur at puberty no disease will manifest in healthy boys and girls. About this time the young people eat excessively, the result being indigestion and impure blood. The changes that occur in the skin make it a favorable place for irritations to manifest. Let the boys and girls eat so that they have bright eyes and clean tongues and there will be very little trouble from disfiguring pimples. Eczema is generally curable by means of proper diet and the same is true of nearly all skin diseases that afflict infants. There are diseases of the skin due to local irritants, such as the various forms of trade eczema, scabies (itch), and pediculosis (lousiness), but the fact remains that nearly all skin diseases fail to develop if the individual eats properly, and most of them can be cured, after they have developed, by proper diet and attention to hygiene generally. If the diet is such that irritants are manufactured in the alimentary tract and absorbed into the blood, and then excreted through the skin, where enough irritation is produced to cause disease, it is useless to treat with powders and salves. Correct the dietetic errors and the skin will cure itself. Specialists in skin diseases often fail because they treat this organ as an independent entity, instead of considering it as a part of the body whose health depends mostly upon the general health. CHAPTER XXII. EXERCISE. Nature demands of us that we use our mental and physical powers in order to get the best results. Man was made to be active. In former times he had to earn his bread in the sweat of his face or starve. Now we have evolved, or is it a partial degeneration, into a state where a sharp mind commands much more of the means of sustenance than does physical exertion. The consequence is that many of those equipped with the keenest minds fail to keep their bodies active. This helps to lessen their resistance and produces early death. Some exercise is needed and the question is, how much is necessary and how is it to be taken so that it will not degenerate into drudgery? There are very few with enough persistence to continue certain exercises, no matter how beneficial, if they become a grind. The amount required depends upon the circumstances. Ordinarily, a few minutes of exercise each day, supplemented with some walking and deep breathing will suffice. About five minutes of vigorous exercise night and morning are generally enough to keep a person in good physical condition, if he is prudent otherwise.