Sweating is one of the human body’s most fundamental and underappreciated functions. On a hot day or during strenuous exercise, it is our primary, built-in air-conditioning system, working silently to regulate our internal temperature and prevent us from overheating. But what happens when this system breaks? This is the reality for individuals with anhidrosis, a rare but serious condition characterized by the inability to sweat normally. While not sweating might sound like a minor inconvenience, it can be extremely dangerous, as it robs the body of its ability to cool itself, leading to a high risk of overheating, heat exhaustion, and life-threatening heatstroke. Understanding this condition is crucial for recognizing its signs and implementing the lifestyle changes necessary to live safely.

Anhidrosis refers to the inability to sweat normally, even when the body is overheated. Sweating is a vital function that helps regulate body temperature. Without it, heat builds up, potentially leading to heat exhaustion or even heatstroke, especially in warm environments or during physical exertion.

Anhidrosis can be localized (affecting a specific part of the body) or generalized (involving most or all of the body). Some people may not notice symptoms until they experience unusual overheating, fatigue, or dizziness in hot weather or while exercising.

It can occur on its own or as a symptom of another condition, such as nerve damage, skin disorders, or certain genetic syndromes. In rare cases, it may be present from birth (congenital).

Analogy: Imagine your body is like a car with a radiator. Sweating acts as your body’s cooling system. In anhidrosis, that radiator is broken, you may not notice it on a cool day, but when things heat up, your system can quickly overheat.

Anhidrosis is not a disease in itself but is almost always a symptom of an underlying medical condition, a side effect of a medication, or the result of an injury. The inability to sweat occurs when something disrupts the complex pathway that controls sweating. This can be a problem with the sweat glands themselves, the nerves that send signals to the glands, or the parts of the brain that regulate body temperature.

The causes are numerous and can be grouped into several categories:

1. Nerve Damage (Neuropathy): This is one of the most common categories of causes. The autonomic nervous system nerves are responsible for sending the “go” signal to the sweat glands. If these nerves are damaged, the signal can’t get through.

• Diabetes Mellitus: Long-term high blood sugar can damage nerves throughout the body, including the autonomic nerves that control sweating. This is a very common cause of patchy or progressive anhidrosis.
• Alcoholism: Chronic, heavy alcohol use can lead to alcoholic neuropathy, which can also impair sweat function.
• Autoimmune Neuropathies: Conditions like Guillain-Barré syndrome or Sjögren’s syndrome can involve the immune system attacking and damaging the autonomic nerves.
• Spinal Cord Injuries: An injury to the spinal cord can interrupt the nerve pathways from the brain to the sweat glands below the level of the injury.

2. Skin Damage and Disease: Sometimes the problem lies directly with the skin and the sweat glands themselves being blocked or destroyed.

• Severe Burns or Trauma: A deep burn or injury can permanently destroy the sweat glands in the affected area of skin.
• Radiation Therapy: Radiation used to treat cancer can damage sweat glands in the treatment field.
• Clogged Ducts (Pori-occlusion): Some skin conditions, like severe miliaria (heat rash) or psoriasis, can physically block the sweat ducts, preventing sweat from reaching the surface.
• Scleroderma: This autoimmune condition causes a hardening of the skin, which can constrict and damage sweat glands.

3. Genetic Conditions: In some cases, a person is born with an inability to sweat because the sweat glands did not develop properly in the first place.

• Hypohidrotic Ectodermal Dysplasia (HED): This is a well-known genetic disorder where individuals are born with few or no sweat glands, in addition to abnormalities of the hair and teeth.
• Fabry Disease: This is a rare genetic disorder of metabolism that can cause a range of symptoms, including reduced sweating.

4. Medications: A number of common medications can interfere with the chemical signaling required for sweating as a side effect. These include:

• Anticholinergics: Drugs used to treat overactive bladder, irritable bowel syndrome, and COPD.
• Tricyclic Antidepressants.
• Some Antipsychotic Medications.
• Certain Blood Pressure Medications, like calcium channel blockers.

In some cases, despite a thorough investigation, a specific cause for the anhidrosis cannot be found. This is known as idiopathic anhidrosis.

Clinically, we see anhidrosis in patients with long-standing diabetes or autoimmune disorders that cause small-fiber neuropathy, often affecting the legs or hands first.

Anhidrosis can be acquired or inherited. Most cases are acquired and result from injury or disease affecting the sweat glands or their nerve supply.

The primary risk factors for developing anhidrosis include:

• Having a diagnosed neuropathy, especially from a common condition like diabetes.
• Having certain genetic disorders known to affect sweat gland development, such as ectodermal dysplasia.
• Being of an older age, as sweat gland function can naturally decline over time.
• Suffering a severe skin injury, like a deep burn.
• Taking medications that are known to have decreased sweating as a potential side effect.

Signs of anhidrosis vary depending on whether the condition is localized or generalized, and whether it’s partial or complete.

The primary sign is a marked lack of sweat. An individual may notice that while others are sweating heavily in a hot environment, their own skin remains completely dry. The symptoms are often not the lack of sweat itself, but rather the body’s reaction to its inability to cool down.

The key signs and symptoms of overheating due to anhidrosis include:

• Dizziness or Lightheadedness: As the core body temperature rises, it can affect brain function and blood pressure.
• Flushed Skin: The skin may become red and feel hot to the touch. This is because the body is trying to compensate by dilating the surface blood vessels to radiate heat away, but this method is far less effective than evaporation.
• Muscle Cramps or Weakness: Heat cramps are an early sign of heat-related illness.
• Nausea and General Discomfort.
• A Rapid, Pounding Pulse: The heart works harder to try to cool the body by pumping more blood to the skin.

One interesting clue is compensatory sweating. If the anhidrosis only affects certain parts of the body, a person might notice that they sweat excessively from the parts that are still working. For example, if the legs and trunk cannot sweat, the face and neck might drip with sweat in an attempt to make up for the deficit.

The inability to sweat can lead to heat exhaustion, which can rapidly progress to heatstroke. Heatstroke is a life-threatening medical emergency requiring immediate intervention. Call for emergency medical help immediately if you or someone else shows these signs:

• High core body temperature (103°F / 39.4°C or higher).
• Confusion, agitation, irritability, or delirium.
• Slurred speech.
• Seizures.
• Loss of consciousness or coma.
• Skin that is hot and flushed but may be dry.

While waiting for emergency help to arrive, move the person to a cool, shaded place and do everything possible to cool them down.

Diagnosis

 A doctor will begin by taking a detailed medical history and performing a physical exam. To confirm the diagnosis and investigate the cause, several tests may be used:

• Thermoregulatory Sweat Test: This is considered the gold standard for diagnosing generalized anhidrosis. The patient is coated in a powder that changes color when it gets wet. They are then placed in a chamber where the temperature and humidity are slowly raised. The pattern of color change on the skin creates a map that clearly shows where the body is and is not producing sweat.
• Skin Biopsy: A small sample of skin may be taken and examined under a microscope to look for abnormalities in the sweat glands or the nerves that supply them.
• Quantitative Sudomotor Axon Reflex Test (QSART): This test measures the function of the autonomic nerves that control sweating in a specific area.
• Other Tests: Depending on the suspected cause, further blood tests, nerve conduction studies, or genetic tests may be ordered.

Treatment

As there is often no way to fix the damaged sweat glands or nerves, management of anhidrosis focuses on two key goals: treating the underlying cause if possible, and, most importantly, preventing overheating.

Cooling Strategies and Lifestyle Modifications: Living safely with generalized anhidrosis requires making significant lifestyle adjustments, especially in hot weather.

• Stay in Cool Environments: Air conditioning is the most effective tool. During hot seasons, it is essential to spend the hottest parts of the day indoors in a climate-controlled environment.
• Avoid Strenuous Activity in the Heat: Exercise should be done in an air-conditioned gym or during the coolest parts of the day (early morning or late evening).
• Wear Appropriate Clothing: Lightweight, loose-fitting clothes made of breathable fabrics are best.
• Simulate Sweating: This is a key strategy. Regularly misting the skin with a spray bottle of cool water can mimic the evaporative cooling effect of sweat. Applying cool, wet towels to the neck, armpits, and groin can also help reduce body temperature.
• Stay Hydrated: Drinking plenty of cool water is essential to help the body manage its temperature, even without sweating.
• Be Prepared: Always carry a water bottle and a spray bottle when going out in warm weather. Recognize the early signs of overheating and immediately seek a cooler environment.

Treating the Underlying Cause: If the anhidrosis is caused by a medication, stopping or changing the drug (always under a doctor’s supervision) may restore normal sweat function. If it is caused by an underlying condition like diabetes, good management of that condition may help prevent neuropathy from worsening.

Anhidrosis is a serious condition that goes far beyond the simple inconvenience of not sweating. It represents the failure of the body’s most critical cooling mechanism, placing individuals at constant risk of dangerous overheating and heatstroke. The key to living with anhidrosis is knowledge and vigilance. A proper diagnosis to identify the underlying cause is the first step. This must be followed by a deep commitment to proactive, preventative strategies, avoiding heat, modifying activity, and using external cooling methods to keep the body’s temperature in a safe range. Patients often say they thought it was “just their body type” until they ended up in the ER during a heatwave. Awareness makes all the difference.

• Harper, C. D., & Bermudez, R. (2023). Anhidrosis. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK555988/
• Cleveland Clinic. (n.d.). Anhidrosis (lack of sweat). Cleveland Clinic. Retrieved June 14, 2025, from https://my.clevelandclinic.org/health/diseases/15891-anhidrosis-lack-of-sweat
• National Institutes of Health, Genetic and Rare Diseases Information Center (GARD). (n.d.). Idiopathic pure sudomotor failure. Retrieved from https://rarediseases.info.nih.gov/diseases/10948/idiopathic-pure-sudomotor-failure
• Mayo Clinic. (2023). Anhidrosis: Symptoms and causes. https://www.mayoclinic.org
• American Academy of Dermatology (AAD). (2023). Sweat gland disorders. https://www.aad.org