The sweat glands discharge on the average from one and one-half to two pounds of perspiration per day, more in hot weather and much less when it is cool. They are distributed over the whole external surface of the body. According to Krause there are almost 2,400,000 of them. They carry off water and carbonic acid gas chiefly.
The functions of the skin are: To protect the underlying structures; to regulate the heat; to serve as an organ of respiration; to serve as an organ of touch and thermal sensation; to secrete and eliminate various substances from the body; to absorb.
The heat regulation is quite automatic. When the external temperature is high there is a relaxation of the skin. The pores open, the perspiration goes to the surface and evaporates, thus cooling the body. When the surface is cool the skin contracts, closing the pores and conserving the heat. Radiation always takes place, except when the temperature is very high.
The sensation of touch and the ability to feel heat and cold protect us from untold numbers of dangers. They are a part of the equipment which enables us to adjust our selves to our environment.
The secretions and excretions are perspiration and sebum. These contain water, carbonic acid, urea, buturic acid, formic acid, acetic acid, salts, the chief being sodium chloride, and many other substances.
The respiratory function consists in the absorption of a small amount of oxygen and the giving off of some carbonic acid.
A small amount of water can be absorbed by the skin. Oils can also be absorbed. In case of malnutrition in children, olive-oil rubs are often helpful. This absorptive function is taken advantage of by physicians who rub various medicaments into the skin. Mercury enough to produce salivation can be absorbed in this way.
From the above it will be seen that the skin is not only complex in structure, but has many functions. It is impossible to have perfect health without a good skin. Under civilized conditions a healthy skin can not be had without giving it some care. The average person has a skin that shows lack of care. Fortunately, but little care is needed.
A bath should be taken often enough to ensure cleanliness. Warm water and soap need not be used more than once or twice a week under ordinary conditions. If the soap causes itching, it is well to use a small amount of olive oil on the body afterwards, rubbing it in thoroughly, and going over the body with a soft cloth after the oil rub, thus removing the oil which would otherwise soil the clothes. If the skin is not kept clean, the millions of pores are liable to be partly stopped up, which results in the retention of a part of the excretory matter within the skin, where it may cause enough irritation to produce some form of cutaneous disorder, or the skin may through disuse become so inactive that too much work is thrown upon the other excretory organs, which may also become diseased from overwork and excessive irritation.
Soaps are irritants. Tallow soaps and olive oil soaps are less irritating than other varieties. Whatever kind of soap is used, it should be rinsed off thoroughly, for if some of it is left in the pores of the skin roughness or even mild inflammation may ensue. Be especially careful about the soap used for babies, avoiding all highly colored and cheap perfumed soaps.