BODY ODOR AND SWEATING

Causes

You have two types of sweat glands in your skin: eccrine glands and apocrine glands. Eccrine glands occur over most of your body and open directly onto the surface of your skin. Apocrine glands develop in association with hair follicles on your scalp, underarms and genitals.

You have between 2 million and 5 million eccrine sweat glands. When your body temperature rises, your autonomic nervous system stimulates these glands to secrete fluid onto the surface of your skin where it cools your body as it evaporates. This fluid (perspiration) is composed mainly of water and salt (sodium chloride) and contains trace amounts of electrolytes — substances that help regulate the balance of fluids in your body.

Apocrine glands, on the other hand, secrete a fatty sweat directly into the tubule of the gland. When you're under emotional stress, the wall of the tubule contracts and the sweat is pushed to the surface of your skin where bacteria begin breaking it down. Most often, it's the bacterial breakdown of apocrine sweat that can cause a strong odor.

A number of factors can affect how much you sweat and even the way your sweat smells. Certain foods, drugs or medical conditions can cause excessive sweating while other drugs or conditions may interfere with your ability to perspire normally.

Excessive sweating (hyperhidrosis)

Some people simply sweat more than others for no apparent reason. But some factors also may make you sweat heavily. These include:

• Certain foods and beverages. Drinking hot beverages and those that contain caffeine or alcohol can make you sweat. Eating spicy foods can do the same thing.

• Certain drugs. Drugs that can cause excessive sweating include some antipsychotic medications used to treat mental disorders, morphine and excess doses of the thyroid hormone thyroxine. Overdoses of analgesics such as aspirin and acetaminophen (Tylenol, and generics) also can cause intense sweating.

• Menopause. Women going through menopause may experience hot flashes — a rise in skin temperature accompanied by sweating and a feeling of intense heat — due to a drop in estrogen levels. Some menopausal women may also be awakened at night by soaking sweats followed by chills. But for many women, treatment with hormone replacement therapy (HRT) can help relieve hot flashes and other symptoms of menopause. Although it's much less common, some men with low levels of the male hormone testosterone or a condition known as hypogonadism — which causes reduced functioning of the testicles — also can have hot flashes.

• Low blood sugar . This occurs when the level of sugar in your blood drops below a certain level. It's most common in people with diabetes who take insulin or oral medications that enhance the action of insulin. Early signs and symptoms include sweating, shakiness, weakness, hunger, dizziness and nausea. Some people also may develop low blood sugar after eating, especially if they've had stomach or intestinal surgery. In rare cases, your body may produce too much of the pancreatic hormone insulin, leading to low blood sugar.

• Fever. A fever occurs when your temperature rises above its normal range. You may have a fever with many types of bacterial and viral infections, ranging from a mild case of the flu to serious illnesses such as pneumonia. When your body temperature finally begins to return to normal, you may sweat profusely, which is your body's way of dissipating the excess heat. Fevers followed by shaking chills may indicate a serious infection.

• Hyperthyroidism (overactive thyroid). Sometimes the thyroid gland produces excess amounts of the hormone thyroxine. This can cause a number of symptoms including weight loss, a rapid or irregular heartbeat, nervousness and increased sensitivity to heat. It may also cause you to perspire much more than normal.

• A heart attack . This occurs when there is a loss of blood supply to your heart muscle. A heart attack can damage or destroy part of your heart muscle and may sometimes be fatal. The symptoms of a heart attack include pressure, fullness or squeezing pain in your chest that lasts for a few minutes or pain that extends beyond your chest to your shoulder, arm or back; shortness of breath and intense sweating. If you experience these symptoms, get immediate medical care. Every minute counts after a heart attack.

• Tuberculosis (TB). This chronic bacterial infection of the lungs affects more than 25,000 people in the United States each year. When left untreated, TB can be fatal. Among its signs and symptoms are a cough, slight fever and night sweats.

• Malaria. Worldwide, more than 200 million people have malaria — a disease that occurs primarily in rural areas of tropical and subtropical countries. About 1,000 new cases are reported each year in the United States, primarily among people returning from other parts of the world. The symptoms are related to the life cycle of the parasite that causes malaria, and may begin anywhere from 8 days to 1 year after you've been infected. Initially, you may have chills, headache, vomiting and nausea, but as your body temperature falls, you begin to sweat profusely. The cycle may recur every 48 or 72 hours. Because malaria infection often resembles the flu, it's easily overlooked. Notify your doctor if you develop any of these symptoms within 12 months of traveling to a region where malaria is common.

Decreased or nonexistent sweating (anhidrosis)

Most people are worried about excessive sweating. But some people sweat very little or not at all — a condition that can be potentially life-threatening. Factors that may affect your ability to perspire normally include:

• Certain drugs. Antipsychotic medications used to treat serious mental disorders may interfere with the functioning of the sweat glands.

• Hypohidrotic ectodermal dysplasia (HED). Children with this rare disorder are born without sweat glands, which puts them at high risk of death from overheating (hyperthermia) — especially in hot environments. So far, scientists have identified two genes that may be responsible for HED.

• Autonomic neuropathy. This disorder damages the nerves that help control some of the involuntary functions of the autonomic nervous system, which regulates your internal organs, sweat glands and blood pressure. In some cases, damage to these nerves interferes with the activity of your sweat glands, making it hard for your body to maintain its normal temperature.

• Infections. Severe infections of the sweat glands — such as hidradenitis — may prevent the glands from functioning normally.

• Burns. Major (third degree) burns — either from fire, chemicals or electricity — can damage the skin as well as sweat glands, muscle and even bone.

• Dehydration. This occurs when you don't have enough water in your body to carry on normal functions. You can easily become dehydrated when you work or exercise in hot weather and don't drink enough fluids to replace what you've lost through perspiration. Other common causes of dehydration include persistent vomiting or diarrhea or the use of medications that increase the flow of urine (diuretics). Eventually, you may have so little water left in your body that you're no longer able to sweat. Signs and symptoms may include thirst, weakness, confusion and even fainting. Severe dehydration can be fatal. Older adults and young children are especially at risk.

• Heatstroke. Like dehydration, heatstroke can occur when you work or exercise strenuously in hot weather and don't drink enough to replace the fluids you've lost. Older adults, people who are obese and children with HED are at high risk of heatstroke. Heatstroke is particularly serious because your body's normal mechanisms for dealing with heat stress, such as sweating, are lost. The main symptom of heatstroke is a high temperature — generally greater than 104 F — with hot, dry skin and confusion or even coma.