Some people sweat more than others, but everybody sweats. The major functions of sweating are to remove unwanted waste products from the body and to help regulate the body’s temperature. Sweating goes on whether you visit the North Pole or bask in the sun on a tropical island. Heat produced by the muscles and by various chemical reactions in the body is taken up by the watery sweat and carried out to the surface of the skin, then discharged into the air when the water evaporates. When it is hotter and the body heat builds up faster, you sweat more. Sometimes so much sweat is produced that it forms visible drops that roll down your face or soak your shirt. (A baseball pitcher working on a hot summer day may sweat out more than a gallon of fluid in a single game.) When it is colder you sweat less, although some sweat is still being formed. Even when you cannot see or feel any wetness on your skin, about three cups of sweat evaporate from your body each day.
Two Types of Sweat Glands
There are two types of sweat glands:
- Eccrine Glands
- Apocrine Glands
The most abundant are the eccrine glands, the sweat glands mainly involved in the body’s temperature – control system. They produce a thin, watery sweat containing water, salts, and a body waste product called urea. The ones in the palms of the hands and the soles of the feet are particularly sensitive to emotions. When you are about to give a speech or bat in a tight ball game or meet someone who is important to you, you are likely to find your palms sweaty.
The apocrine glands, the other type, are found only in the armpits, genital area, and nipples and typically empty into hair follicles. The secretion of apocrine sweat glands is a sticky white,gray, or yellowish fluid containing a number of complicated chemicals. This kind of sweat is a part of a communicating system that humans do not use very much (at least, not consciously) but many of our animal relatives depend on: communication by scent messages. Each person (or animal) has a characteristic “odor signature,” produced by chemicals in the breath and various body secretions. This odor may vary, depending on a person’s physical condition or emotional state as well as various body cycles. Animals use scent to mark off their home territories and to announce to other members of their species that they are ready to mate. Scientists are not sure yet how much of a role scent plays in human life, but they do know that the sweat from the apocrine glands is the main component of “body odor.”
The apocrine glands do not become active until puberty. So, although young children sweat, their perspiration doesn’t have the “smelly” odor typical of adults. Actually, it is not the sweat itself that smells.The odor results from the action of bacteria that grow on the sweat. Apocrine sweat is smellier than eccrine sweat because it contains much larger amounts of organic chemicals (good bacteria food). Body hairs also help to trap moisture close to the skin and provide more surfaces for bacteria to grow on—and the places where apocrine sweat glands are found are usually rather hairy. Bacteria grow and multiply faster in hot temperatures, which is why your underarms are smellier in the summer than in the winter.
Functions of Sweating
In addition to cooling the body and getting rid of wastes, sweat helps to lubricate the skin cells on the outer epidermis and keeps them from being worn away too quickly.
The skin is also lubricated by another type of gland found in the dermis, the oil, or sebaceous, glands. Sebaceous glands are found in the skin of many parts of the body, but they are concentrated mostly on the face, neck, upper chest, and back. In some areas of the face there are about two thousand oil glands per square inch! There aren’t any oil glands on your lips, the palms of your hands, or the soles of your feet—areas that are completely hairless. (But anyone who has ever had sweaty palms or sweaty feet knows there are plenty of sweat glands there.)