Perspiration is the process by which fluid leaves the body through the sweat glands in the skin. This fluid can also be called perspiration, or sweat.  Sweating is the body’s response to heat, strenuous exercise or emotional stress.

According to the American Academy of Dermatology, sweat is 55 to 60 percent fluid, mostly water. Sweat also contains sodium chloride (salt) and tiny amounts of other substances, including potassium, calcium, lactic acid and phosphorus. When these substances exist in fluid they are called electrolytes and help regulate the balance of fluids in the body. Sodium chloride and phosphorus cause sweat to sting the eyes upon contact and also give it its salty taste. Sweat also contains trace amounts of such waste products as ammonia and urea.

Sweat glands are long, coiled, hollow tubes of cells. Millions of sweat glands are located throughout the surface of the body.  The external sex organs, lips and external ear canal are the only areas without sweat glands. The coiled base of sweat glands is located in the second layer of skin (dermis). Sweat is produced in the glands and carried to the surface of skin by tiny ducts that attach to the pores (tiny holes in the skin).

There are two types of sweat-producing glands:

• Eccrine glands. These glands are located throughout the skin, but the highest concentrations are found in the palms of the hands, soles of the feet and forehead. Eccrine glands open directly to the pores in the skin. They are active throughout a person’s life and produce sweat when a person is hot, stressed or feeling strong emotions. Eccrine glands are the most abundant type of sweat gland.
  
  
• Apocrine glands. These sweat glands become active when a person reaches puberty. Apocrine glands connect to the skin through hair follicles. They are located in areas with many hair follicles, concentrated in the underarms and genital region, with some on the scalp and around the nipples. Sweat from apocrine glands is mixed with fatty acids and proteins to produce a thick, oily sweat when a person is under stress or experiencing strong emotions.
  
  

  

Sweat does not have a bad odor. When it reaches the skin, however, sweat interacts with the bacteria normally present on the skin and begins to break down, which can produce an unpleasant odor. Many people use commercial deodorant or antiperspirant products to mask or reduce the smell of underarm perspiration.