The body has several mechanisms to control the internal temperature. Heat is generated by the body’s cells as part of its metabolic activity. At the same time heat is lost through the surface of the skin into the environment. The heat will dissipate faster if the body is unclothed or when the environment is cold and slower if a person is tightly covered by clothing and the environment is warmer. One of the important mechanisms to control the body temperature is the secretion of sweat. This salty fluid is released by the eccrine sweat glands in the skin and as it evaporates it cools the surface and therefore the body. The amount of sweat is regulated by the central nervous system.
The hypothalmic-preoptic area in the brain (thermoregulatory center) can send nerve impulses by way of the autonomic system to increase activity of the sweat glands. This is also influenced to some degree by the emotional state. Local reflexes also participate in this process when only one part of the body is exposed to heat by sending impulses to the spinal cord which then signals the sweat glands in the area to become active. Sweating, or perspiration, is the process of releasing fluid onto the surface of the skin so that the evaporation can cause a cooling effect.
The degree of sweating is determined to some extent by the number of sweat glands in the skin. There is approximately two and a half million sweat glands in the skin with men having more of these glands than women. It is usually carefully regulated but in certain physiological and pathological situations it may increase or decrease to an extent that is not necessary.
There are two important terms associated with excessive perspiration – hyperhidrosis and diaphoresis. The terms are often used interchangeably.
What is hyperhidrosis?
Hyperhidrosis is the medical term for excessive sweating despite the lack of appropriate stimuli like hot and humid weather. It is usually associated with overactivity of the sympathetic nervous system. Hyperhidrosis can sometimes arise with local pathology that affects the body’s thermal receptors or associated nervous components. Usually there is no significant increase in body temperature to warrant the excessive sweating. Hyperhidrosis can be primary where it occurs with no other conditions or secondary in that it is associated with other diseases.
What is diaphoresis?
Diaphoresis is the excessive sweating that is seen with certain diseases. It may also be referred to as secondary hyperhidrosis. It is noted as a symptom of these diseases and often a result of malfunctioning temperature regulation. Diaphoresis may also be related to raised body temperature seen with these diseases, particularly febrile illnesses.
Other Signs and Symptoms
The excessive sweating may be localized (focal) or generalized. The forehead, palms (palmar hyperhidrosis), soles of the feet and underarms (armpits) are the more common sites of focal sweating. Gustatory sweating is a type of focal sweating around the mouth and lips that occurs with eating. In generalized sweating, perspiration occurs throughout the body.
Higher body temperature may be associated with fever of unknown causes or in infections, raised metabolic activity due to drugs or increased thyroid activity.
Chest pain, cold clammy skin, paleness and dizziness may be seen with excessive sweating in cardiovascular causes.
Excessive sweating is more often profuse at night (nocturnal / night sweats) but this is more prominent in certain diseases like tuberculosis, infective endocarditis and in HIV. Lymphoma and leukemia may also present with night sweats.
Causes of Excessive Sweating
Most cases of primary hyperhidrosis is idiopathic – meaning that there is no known cause for the excessive sweating. There are no other symptoms and is often difficult to treat. It is almost always chronic and starts from early childhood or even the teen years and persists throughout life.
In psychological causes, excessive sweating may be associated with overactivity of the sympathetic nervous system despite the body temperature being normal.
- Emotional stress
- Nervous disposition
- Hot environmental conditions
- Excessive physical activity
- Spicy foods
Medication and substances
- Weight loss drugs
- Drugs with caffeine
- Antidiabetic medication
- Opiate withdrawal
- Hyperthyroidism (thyrotoxicosis)
- Diabetes mellitus (hypoglycemic attacks)
- Carcinoid syndrome – hormone secreting tumors
- Tuberculosis (TB)
- Infective endocarditis
- Systemic infections including HIV and opportunistic infections
- Severe trauma, especially head trauma
- Heart attack (myocardial infarction)
- Autonomic neuropathy
- Peripheral neuropathy
- Parkinson’s disease
- Spinal cord injury