Hypohidrosis is a condition that causes a person to sweat less than usual. Sweating helps the body to cool down, and insufficient sweating can lead to heat-related illnesses such as heat exhaustion.
Hypohidrosis is a less severe form of anhidrosis, where a person is entirely unable to sweat. It is also possible for a person to sweat excessively, a condition known as hyperhidrosis.
In this article, we discuss the additional symptoms of hypohidrosis as well as possible causes and treatments.
A person with hypohidrosis is less able to sweat. This means that the body is less effective at cooling down. The condition often causes parched skin, intolerance to heat, and a general feeling of being unwell.
A person with hypohidrosis is most likely to experience symptoms when they are exercising or experiencing high temperatures.
Symptoms of hypohidrosis include:
- very dry skin
- skin flushing
- inability to tolerate heat
- inability to tolerate physical exertion
- feeling excessively hot
- labored breathing
- muscle cramps or weakness
Hypohidrosis occurs due to poorly functioning sweat glands. Ordinarily, as body temperature rises, the autonomic nervous system stimulates the sweat glands which then release moisture onto the skin's surface. The evaporation of the sweat cools the skin.
A localized skin condition or injury can damage the sweat glands, leading to reduced sweating. Hypohidrosis may also be one of the symptoms of an immune or neurological condition.
Some people may have idiopathic hypohidrosis, which is hypohidrosis that occurs with no known cause.
Some causes of hypohidrosis are listed below:
Skin conditions and injuries
Hypohidrosis that results from skin conditions and injuries usually affects a single area of the body. If the affected area is small, then the condition should not be cause for concern. This is because sweat glands in other areas of the body will compensate to keep the person cool.
The most common causes of localized hypohidrosis include:
- clogged sweat ducts (poral occlusion)
- bacterial infections
- injury, especially burns
Certain inflammatory skin conditions can also impair sweat gland function. These include:
In addition, some conditions that primarily affect other parts of the body may cause hypohidrosis and other abnormalities of the skin. Examples include the immune system conditions Sjogren's syndrome and graft-versus-host disease (GvHD).
If a person has lost more fluid than they have taken in, they will lack the moisture they require to sweat.
The following medications can interfere with sweat gland function:
- antipsychotic medications
- anticholinergic drugs
- calcium-channel blockers
If someone thinks that a particular medication is causing their hypohidrosis, they should speak to a doctor. They should never adjust their dosage or stop taking medication of their own accord.
In some cases, hypohidrosis can occur as a result of damage to the nerves that control sweating.
Sometimes this damage will be due to an underlying disorder involving the central nervous system, which consists of the brain and spinal column.
Some examples include:
- multiple system atrophy (MSA)
- multiple sclerosis (MS)
- parkinson's disease
- dementia with Lewy bodies (DLB)
Disorders involving the peripheral nervous system can also cause hypohidrosis. These include:
- Ross syndrome, a genetic disorder that can cause either hypohidrosis or hyperhidrosis
- Harlequin syndrome, which involves sweating more on one side of the body than the other
- diabetes mellitus
- Guillain-Barré syndrome
- B-vitamin deficiency
- alcohol use disorder (AUD)
A person may inherit a defective gene that causes the sweat glands to function poorly or not at all. People affected by a rare genetic condition called hypohidrotic ectodermal dysplasia (HED) are born either without sweat glands or with very few functional sweat glands.
To diagnose hypohidrosis, the doctor will need to make a thorough assessment of the person's medical history. People who suspect that they have hypohidrosis may wish to keep a written record of any activities that cause symptoms.
A doctor may perform the following tests to diagnose hypohidrosis and to establish its underlying cause.
- Thermoregulatory skin test. This involves coating the person's body in a powder that changes color when the skin releases sweat. They then enter a chamber that causes the body temperature to rise to a level that should promote sweating. If the powder does not change color in the areas of the body that produce sweat, this indicates an absence of sweating.
- Quantitative sudomotor axon reflex test (QSART). This test assesses the function of the nerves that regulate sweating. During the test, electrodes stimulate the sweat glands, and a doctor measures the volume of sweat that the body produces.
- Silastic sweat imprint test. This test also assesses nerve function in response to electrical stimulation of the skin. The individual sweat droplets imprint onto a material made of silicone rubber.
- Skin biopsy. If a doctor suspects that a skin condition is causing the hypohidrosis, they may perform a biopsy. This involves removing some skin and sweat glands and sending them to a lab for examination under a microscope.
- MRI of the brain or spinal cord. An MRI scan may be necessary if a doctor suspects that a problem with the central nervous system is responsible for the hypohidrosis.
One of the biggest risks of hypohidrosis is the development of heat stroke. Heat stroke is a serious and potentially fatal medical condition.
If a person suspects that they have heat stroke, they should phone the emergency services immediately. Symptoms of heat stroke include:
- intense thirst
- a headache
- dizziness and confusion
- fast breathing or rapid pulse
- nausea and loss of appetite
- cramps in the arms, legs, and stomach
The treatment of hypohidrosis will depend on its underlying cause. If the cause is due to another medical condition, hypohidrosis may improve once a person begins treatment for that condition.
A 2013 review outlining approaches to diagnosing and treating hypohidrosis recommends that people manage the condition by doing the following:
- Avoiding drugs that can aggravate hypohidrosis, which may include anticholinergics and opioids.
- Limiting activities that raise the core body temperature.
- Performing exercises under supervision and in a cool, well-ventilated environment.
Below are some additional tips on how to keep the core body temperature within safe limits:
- taking regular cool showers
- using a cool mist humidifier indoors
- wearing loose-fitting clothing
- wearing damp clothing in hot weather
- applying damp flannels to the skin
- avoiding over-exertion, particularly in hot weather
Hypohidrosis that affects only a small area of the body should not be cause for concern.
When the condition affects large areas of the body, it can severely impair a person's ability to keep cool.
If this is the case, a person should speak to their doctor, especially if they have additional risk factors for other medical conditions. A doctor will conduct diagnostic tests with the aim of developing a tailored treatment plan.
Hypohidrosis can occur as an isolated case, or as a symptom of another medical condition.
Treatment options will vary depending on the underlying cause.
Managing hypohidrosis entails taking steps to prevent the core body temperature from becoming dangerously elevated. This will reduce the risk of a more severe heat-related condition such as heat stroke.