Apocrine sweat glands are restricted to the armpits and a few other areas of the body and produce an odorless, oily, opaque secretion which then gains its characteristic odor from bacterial decomposition.

In humans, sweating is primarily a means of thermoregulation, which is achieved by the water-rich secretion of the eccrine glands.

Animals with few sweat glands, such as dogs, accomplish similar temperature regulation results by panting, which evaporates water from the moist lining of the oral cavity and pharynx.

[8] In horses, such cooling sweat is created by apocrine glands[9] and contains a wetting agent, the protein latherin which transfers from the skin to the surface of their coats.

Some causes of diaphoresis include physical exertion, menopause, fever, ingestion of toxins or irritants, and high environmental temperature.

If it is accompanied by unexplained weight loss, fever/chills, or by palpitations, shortness of breath, unconsciousness, fatigue, dizziness, muscle pain, nausea, vomiting, diarrhea, and chest discomfort, it suggests serious illness.

Diaphoresis is also seen in an acute myocardial infarction (heart attack), from the increased firing of the sympathetic nervous system, and is frequent in serotonin syndrome, which can result in serious sickness or even death.

Diaphoresis can also be caused by many types of infections, often accompanied by high fever and/or chills which can trigger the result of hyperthermia.

[17] Diabetics relying on insulin shots or oral medications may have low blood sugar (hypoglycemia), which can also cause diaphoresis.

Diaphoresis due to ectopic catecholamine is a classic symptom of a pheochromocytoma, a rare tumor of the adrenal gland.

Acetylcholinesterase inhibitors (e.g. some insecticides) also cause contraction of sweat gland smooth muscle leading to diaphoresis.

In severe cases, botulinum toxin injections or surgical cutting of nerves that stimulate the excessive sweating (endoscopic thoracic sympathectomy) may be an option.

It is important to distinguish night sweats due to medical causes from those that occur simply because the sleep environment is too warm, either because the bedroom is unusually hot or because there are too many covers on the bed.

Sweating is controlled from a center in the preoptic and anterior regions of the brain's hypothalamus, where thermosensitive neurons are located.

[citation needed] Sweating causes a decrease in core temperature through evaporative cooling at the skin surface.

[citation needed] There are two situations in which the nerves will stimulate the sweat glands, causing perspiration: during physical heat and during emotional stress.

The volume of water lost in sweat daily is highly variable, ranging from 100 to 8,000 millilitres per day (0.041 to 3.259 imp fl oz/ks).

[citation needed] Horses have a thick, waterproofed, hairy coat that would normally block the rapid translocation of sweat water from the skin to the surface of the hair required for evaporative cooling.

[2] Many other trace elements are also excreted in sweat, again an indication of their concentration is (although measurements can vary fifteenfold) zinc (0.4 milligrams/litre), copper (0.3–0.8 mg/L), iron (1 mg/L), chromium (0.1 mg/L), nickel (0.05 mg/L), and lead (0.05 mg/L).

[31] In 2001, researchers at Eberhard-Karls University in Tübingen, Germany, isolated a large protein called dermcidin from skin.

This protein, which could be cleaved into other antimicrobial peptides, was shown to be effective at killing some species of bacteria and fungi that affect humans, including Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, and Candida albicans.

[36] However, sweat as a diagnostic fluid presents numerous challenges as well, such as very small sample volumes and filtration (dilution) of larger-sized hydrophilic analytes.