Perspiration is an essential body function and the amount of sweat varies from person to person. The amount of sweat glands a person has directly effects how much they sweat. Although women have more sweat glands then men, men have sweat glands that are more active.

Certain other factors (e.g., heredity, foods, drugs, medical conditions) can also affect how much a person sweats. Sometimes these factors may cause either excessive perspiration (hyperhidrosis) or little or no perspiration (anhidrosis).

Although it can be embarrassing, hyperhidrosis is generally not a cause for concern. Some situations of excessive perspiration are quite common. Hot or alcoholic beverages or spicy foods can make a person sweat more. Some foods may even affect the smell of a person’s sweat. In addition, people with fevers have elevated body temperatures. When a fever breaks and begins to lessen, perspiration can help return the temperature to normal.

If a person suddenly begins to sweat more than usual or if the sweating is accompanied by fever, weight loss, chest pain, shortness of breath or a rapid heartbeat, a patient should seek medical attention immediately. In such cases, hyperhidrosis may be a sign of an underlying illness (e.g., hyperthyroidism). It can also occur as a natural part of the body's processes, such as menopause.

People should also contact their physician when they notice a change in their body odor (e.g., fruity, ammonia-like). Certain changes in body odor may indicate an underlying medical condition.

Lack of perspiration, or anhidrosis, can be potentially life threatening. Some people are born with a rare genetic disorder that results in a lack of sweat glands (ectodermal dysplasia), which causes anhidrosis. These patients require a cooler climate and may require frequent cooling water baths or sprays to maintain a normal body temperature. Other factors that may cause anhidrosis include the use of certain drugs (e.g., antipsychotic medications, diuretics), a severe infection of the sweat glands (hidradenitis) and not drinking enough fluids.

Generally, anhidrosis can severely compromise the body’s ability to cool down and may put a person at risk for hyperthermia (dangerously high body temperature or overheating), especially in hot environments. When a person stops sweating or does not perspire enough to cool the body, the results can be fatal.

Complications of anhidrosis include:

• Heat exhaustion. This often occurs because of excessive exercise and not enough fluid intake (dehydration). The signs and symptoms of heat exhaustion include faintness, nausea, a rapid heartbeat, ashen (pale) appearance and hot, dry skin. A person with these symptoms should cool down immediately by getting into the shade (if outdoors) and drinking tepid fluids. This condition can quickly progress to heatstroke.
  
  
• Heatstroke. A severe condition that can lead to shock, brain damage, organ failure and death. The first signs of heatstroke include severe confusion, bizarre behavior, seizures (sometimes) and coma. A person with this condition requires emergency medical care.

To prevent these complications, it is essential to drink plenty of fluids, particularly water. Fluids containing caffeine, high amounts of sugar, carbonation or alcohol should be avoided or minimized because these liquids tend to have a dehydrating effect on the body.

Keeping hydrated is especially important when exercising, as several quarts of fluid can be lost through perspiration during long periods of vigorous activity. A person should drink fluids before, during and after engaging in exercise to keep the body hydrated. People should also limit outdoor activities to cooler parts of the day (e.g., early morning, early evening) when temperatures are high. Wearing cotton clothing that is loose-fitting and lightly colored can also help people stay cool.