Anhidrosis

Definition

Anhidrosis is the inability to sweat normally. While this may not sound like a serious condition, anhidrosis can be life-threatening. When you don't perspire, your body can't cool itself, which can lead to overheating and sometimes to heatstroke — a potentially fatal condition.

Anhidrosis — sometimes called hypohidrosis — can be difficult to diagnose. Mild anhidrosis often goes unrecognized, and dozens of factors can cause the condition, including skin trauma and certain diseases and medications.

Treatment of anhidrosis involves addressing the underlying cause, if one can be found.

Symptoms

Signs and symptoms of anhidrosis include:

• Little or no perspiration
• Dizziness
• Muscle cramps or weakness
• Flushing
• Feeling hot

A lack of perspiration can occur:

• Over most of your body
• In a single area
• In scattered patches

Unaffected areas may try to compensate by producing more perspiration, so it's possible to sweat profusely on one part of your body and very little or not at all on another. Anhidrosis that affects a large portion of your body prevents proper cooling, so vigorous exercise, hard physical work and hot weather can cause heat cramps, heat exhaustion or even heatstroke.

Anhidrosis can develop on its own or as one of several signs and symptoms of another disorder, such as diabetes, neuropathy or psoriasis.

When to see a doctor
If you barely sweat, even when it's hot or you're working or exercising strenuously, talk to your doctor. Because anhidrosis increases your risk of heatstroke, seek medical care if you develop any signs or symptoms of a heat-related illness, such as:

• Weakness
• Nausea
• Dizziness
• Rapid heartbeat
• Goose pimples on the skin, despite warm temperatures

Causes

Anhidrosis occurs when your sweat glands stop working, and this can happen for a number of reasons, including:

• Nerve damage. Your autonomic nervous system regulates involuntary actions such as digestion, heartbeat, blood pressure and body temperature. Injuries to your nerves that control this system can affect the functioning of your sweat glands.

  Many illnesses can damage your autonomic nerves, including diabetes, alcoholism, Parkinson's disease, amyloidosis — a serious disease that occurs when substances called amyloid proteins build up in your organs — Sjogren's syndrome, which causes dry eyes and mouth, and small cell lung cancer. Anhidrosis is the hallmark of Ross syndrome, a peripheral nerve disorder.

  Rare metabolic disorders, such as Fabry disease, also are associated with anhidrosis. Horner syndrome, which damages nerves in your face and eye, usually causes anhidrosis on the affected side of your face.

• Skin damage. Physical injury to your skin, especially from severe burns, can permanently damage your sweat glands.
• Certain medications. Many prescription medications — including some heart and blood pressure medications, bladder control drugs, nausea medications and psychiatric medications — can reduce sweating. Perspiration usually returns to normal when the medications are stopped. If you develop anhidrosis after starting a new medication, let your doctor know.
• Genetic factors. Some children have genetic disorders that cause sweat glands to malfunction. Others may have an inherited disorder called hypohidrotic ectodermal dysplasia that causes the body to develop with few if any sweat glands.

• Dehydration. This occurs when your body doesn't have enough fluids to carry out its normal functions. In the most serious cases, dehydration can interfere with your ability to sweat. Dehydration is common when you have an intense bout of diarrhea and vomiting, when you have a very high fever, or when you sweat excessively and don't replace lost fluids.

  Dehydration can also occur when you have increased urination — often as a result of undiagnosed or uncontrolled diabetes mellitus or diabetes insipidus.

  Alcohol and certain medications — diuretics, antihistamines, blood pressure medications and some psychiatric drugs — can cause dehydration as well.

Risk factors

Certain factors make anhidrosis more likely, including:

• Age. As you grow older, your ability to sweat normally may diminish, usually because your body has more trouble regulating its temperature.
• Certain health problems. Any medical condition that damages your autonomic nerves makes sweat gland problems more likely. Diabetes is a common condition that can cause nerve damage, but a number of other diseases can injure both nerves and sweat glands, often in a specific area, such as your legs or face.
• Skin disorders. Many diseases that irritate or inflame the skin also affect the sweat glands. Anhidrosis can occur with a number of skin disorders, including psoriasis; exfoliative dermatitis, which is marked by severe skin scaling; heat rash; scleroderma, which causes hard, tight skin; and ichthyosis — extremely dry, scaly skin.
• Genetic abnormalities. Mutations in certain genes can lead to disorders that affect the sweat glands.

Complications

Heat-related illnesses are the most serious complications of anhidrosis. Children are especially vulnerable because their core temperature rises faster than an adult's does, and they dissipate heat less efficiently. All children should be monitored closely for overheating, but extra precautions should be taken when a child has anhidrosis.

Heat-related problems include:

• Heat cramps. These muscle spasms, which can tighten muscles in your legs, arms, abdomen and back, are generally more painful and prolonged than are typical nighttime leg cramps.
• Heat exhaustion. Symptoms such as weakness, nausea and a rapid heartbeat usually begin after strenuous exercise. Anyone with heat exhaustion should be monitored carefully because symptoms can quickly become worse.
• Heatstroke. This life-threatening condition occurs when your body temperature reaches 104 F (40 C) or higher. If not treated immediately, heatstroke can cause hallucinations, loss of consciousness, coma and even death.

Preparing for your appointment

You're likely to start by seeing your family doctor or a general practitioner. However, you may then be referred to a doctor who specializes in skin disorders (dermatologist).

Because appointments can be brief, and there's often a lot of ground to cover, it's a good idea to arrive well prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as modify your diet.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins and supplements that you're taking.
• Ask a family member or friend to come with you, if possible. Sometimes it can be difficult to remember all of the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For anhidrosis, some basic questions to ask your doctor include:

• Why don't certain parts of my body sweat?
• Do I need any tests?
• What caused this condition?
• Will I always have this condition?
• What treatments are available, and which do you recommend?
• I have another health condition; how can I best manage them together?
• Are there any activity restrictions that I need to follow?
• Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

• When did you first notice that you weren't sweating?
• What parts of your body don't perspire?
• Are you experiencing any other symptoms?
• Does anything seem to improve your symptoms?
• What, if anything, appears to worsen your symptoms?
• Did you first notice symptoms when you changed a medication or were diagnosed with another illness?

Tests and diagnosis

Your doctor is likely to suspect anhidrosis based on your signs and symptoms, a thorough medical history and physical exam, but you may need certain tests to confirm the diagnosis. These include:

• Reflex test. In a test called a quantitative sudomotor axon reflex test (QSART), a small, painless electrical current passes through four electrodes placed on your forearm, foot and leg to activate the nerves that supply your sweat glands. The volume of sweat produced by this stimulation is then measured. You may feel a mild tingling or slight burning sensation during the test.
• Silastic sweat imprint. This test measures the distribution of perspiration by taking an imprint of drops of sweat in a rubbery material (Silastic).
• Thermoregulatory sweat test. During this test, you're coated with a powder that changes color when you sweat. You then enter a chamber that causes your body temperature to increase to a level that makes most people perspire. Digital photos document the results.

Sometimes the cause of anhidrosis or hypohidrosis is never found.

Treatments and drugs

Treatment isn't always necessary
Anhidrosis that affects a small part of your body usually isn't a problem and doesn't need treatment. But, large areas of decreased perspiration can be life-threatening. Although there's no specific treatment for anhidrosis itself, treatments may be available for the cause of the problem rather than for anhidrosis specifically.

Treating heat-related problems
Anyone who is overheated needs prompt treatment to prevent symptoms from becoming worse.

Heat cramps
To relieve cramping:

• Rest and cool down.
• Drink cool fruit juice or a sports drink that contains electrolytes.
• Get medical care if cramps become worse or don't go away in about an hour.
• Wait at least several hours before returning to strenuous activity.

Heat exhaustion
When someone develops symptoms of heat exhaustion, such as nausea, dizziness and a rapid heartbeat, act quickly:

• Move the person into a shady or air-conditioned space, and elevate his or her legs slightly.
• Loosen the person's clothing, and remove any heavy pieces of clothing.
• Have the person drink cool, not ice, water or a sports drink that contains electrolytes.
• Spray or sponge the person with cool water.
• If symptoms don't improve quickly, call 911 or emergency medical help.

Heatstroke
Heatstroke requires immediate medical care. This condition can be fatal if left untreated. Until help arrives:

• Move the person into the shade or an air-conditioned space.
• Start the cooling process by spraying the skin with water or wrapping the person in wet towels or sheets, and use a fan or newspaper to increase air circulation.

Prevention

Anhidrosis itself often can't be prevented, but serious, heat-related illnesses can. To stay safe:

• Wear loose, light clothing when it's warm.
• Don't overdress when it's cold.
• Stay indoors on hot days.
• Don't overdo it. Monitor your activity level closely.
• Learn more. Know the signs of heat-related illness and how to treat them.