See your doctor if you suddenly begin to sweat more than usual or experience night sweats for no apparent reason. A cold sweat is usually your body's response to a serious illness, anxiety or severe pain. Seek immediate medical attention for a cold sweat if you have signs of lightheadedness or chest and stomach pains.

Also talk to your doctor if you notice a change in body odor — it may be a sign of certain medical conditions. A fruity smell, for example, may be a sign of diabetes and an ammonia smell could indicate liver or kidney disease. In addition, a rare condition known as fish-odor syndrome (trimethylaminuria), causes an odor similar to rotting fish. People with fish-odor syndrome have a defective gene that prevents them from metabolizing trimethylamine (TMA), a natural byproduct of the digestion of foods such as saltwater fish, eggs and liver.

• Anxiety
• Jock itch

Complications associated with too much or too little sweating can range from annoying to life-threatening. Common complications of excessive sweating include:

• Fungal nail infections. People who sweat profusely are prone to many types of fungal infections. That's because fungi thrive in warm, moist environments such as sweaty shoes. That's also why you're more likely to get an infection in your toenail than in your fingernail. A nail infection usually begins as a white or yellow spot under the tip of your nail. As the fungal infection spreads deeper, your nail may discolor, thicken and develop crumbling edges. Sometimes your nail may separate from the nail bed, and the skin around it may become red and swollen. You may even detect a slight odor.

• Athlete's foot. Sometimes sweaty feet just smell bad. That unmistakable foot smell, which occurs when sweat and bacteria mix, may or may not occur along with athlete's foot — a fungal infection that usually begins between your toes and causes your skin to itch, burn and crack. Athlete's foot can also affect the soles and sides of your feet, causing your skin to peel or thicken.

•  Jock itch. This fungal infection causes an itching or burning sensation around your groin. You may also have a red rash on your inner thighs and buttocks. Jock itch is mildly contagious and can spread by contact or shared towels.

• Bacterial infections and warts. Excessive sweating can contribute to bacterial infections, especially between your toes. It can also lead to warts — skin growths caused by the human papillomavirus (HPV).

• Heat rash or prickly heat. This rash occurs when the pores around the sweat glands become blocked. As a result sweat becomes trapped under your skin, causing fine red spots or bumps — usually on the upper back, chest or arms. It most often occurs in hot, humid weather and generally affects babies and young children. Heat rash can also occur if your baby is dressed too warmly or has a fever.

• When you stop sweating or don't perspire enough to cool your body, the results can be serious or even fatal. Complications of a lack of perspiration include:

•  Heat exhaustion. This can occur suddenly, often because of excessive exercise and inadequate fluid intake. The signs and symptoms include faintness, nausea, a rapid heartbeat, ashen appearance and hot, dry skin. If you have heat exhaustion, you need to cool down immediately by getting into the shade and drinking cool — not cold — fluids. Heat exhaustion can quickly progress to heatstroke.

• Heatstroke. 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. In some cases, heatstroke can be fatal. The main signs and symptoms of heatstroke are a high temperature, hot dry skin and confusion or even coma.

For some people who sweat excessively, the answer may be simple: an over-the-counter (OTC) antiperspirant used on the hands and feet as well as the underarms. Antiperspirants block your sweat ducts with aluminum salts, thereby reducing the amount of perspiration that reaches your skin. Deodorants, which can eliminate odor but not perspiration, turn your skin acidic, which makes it less attractive to bacteria. Although you may have heard stories linking antiperspirants and breast cancer, there's no evidence of such a link.

• Breast cancer

Antiperspirants can cause irritation or even contact dermatitis — red, swollen, itchy skin. In fact, antiperspirants are the cosmetic product most associated with skin irritation. Deodorants, especially herbal or crystal deodorants, may be less irritating for most people.

If OTC products aren't strong enough, your doctor may suggest a prescription antiperspirant. For more severe problems with sweating, he or she may recommend other treatments, including:

• Iontophoresis. In this procedure, a dermatologist uses a battery-powered device to deliver a low current of electricity to the affected area. Although iontophoresis is painless and quite safe, it may be no more effective than a topical antiperspirant.

• Botulinum toxin (Botox). This is the same product that helps smooth facial wrinkles by paralyzing certain muscles. Researchers have discovered that Botox injections are also an effective way to treat severe hyperhidrosis by blocking the nerves that trigger the sweat glands. Botox isn't a cure-all, however. It may take several injections to achieve the desired results, the treatment can be painful, and the results only last about 4 months. In addition, although Botox stops sweating, it doesn't prevent body odor.

•  Surgery. In rare cases surgery may be an option. If excess sweating occurs just in your armpits, removing the sweat glands may help. Another procedure involves cutting the nerves that carry the messages from the sympathetic nerves to the sweat glands. At one time this was a major operation, requiring large incisions in the chest or back to reach the spinal column, where the nerves are located. You typically stayed in the hospital a week and could expect to spend a month recovering. But today the surgery can be performed laparoscopically using a procedure known as endoscopic thoracic sympathectomy. It requires just three small incisions for a video telescope and small surgical instruments. Although the operation is delicate, it typically requires only a day in the hospital and produces minimal scarring. Following the surgery, sweating on the hands permanently stops. But increased sweating can occur elsewhere on your body, such as your back or the back of your legs.