A reduction in sweating (hypohidrosis) or absence of sweating (anhidrosis) can be a concerning symptom. A lack of sweating can be localized or generalized and can produce symptoms of feeling flushed and overheated. When severe, it may lead to complications such as heat exhaustion or heat stroke.
The causes of a lack of sweating (perspiration) may be hereditary or acquired and can include skin conditions, connective tissue diseases, conditions affecting the central or peripheral nervous system, or even medications. While some treatments are available, prevention is the key to prevent complications.
Sweat Glands and Control of Sweating
Sweating via the sweat glands is the body’s most important method of regulating body temperature. In fact, when the air temperature is higher than our skin temperature, the evaporation of sweat is the only means for the body to reduce body temperature and prevent overheating.
When the body temperature becomes too hot, it is sensed by the hypothalamus in the brain. The hypothalamus, in turn, sends signals (via the sympathetic nervous system) to the sweat glands to increase sweat production.
In addition to medical conditions that can affect sweating (discussed below), how the body controls sweating can vary based on factors such as acclimation (how well the body has adjusted to increased heat), elevation, fluid status in the body (such as whether dehydration is present) and more.
There are three primary types of sweat glands—eccrine, apocrine, and apoeccrine. Of these, eccrine sweat glands are of greatest importance in regulating body temperature.
Eccrine glands are present all over the body, but concentrated more heavily on the palms of the hands and soles of the feet. Sweat production begins at around the age of 2 or 3 and continues throughout life.
The number of sweat glands remains the same throughout life. This means that people who are larger or obese have less sweat gland density than those who are small or of normal weight. That said, variation in sweating between different people depends more on the amount of sweat produced each gland than on the number of sweat glands present.
The average sedentary person sweats around 450 milliliters of water in a day, which mostly goes unnoticed. This can increase up to 1.2 liters of sweat hourly in athletes (and be quite noticeable). Exercise and heat acclimation can increase the sweating response, whereas dehydration can have the opposite effect.
Sweating is the body’s primary method of regulating body temperature.
Types and Definition
A lack of sweating may be localized, affecting only certain regions of the body, or generalized. It may also be compensatory as the body responds to increased sweating (hyperhidrosis) in one part of the body by decreased sweating in another.
The incidence of hypohidrosis or anhidrosis is currently unknown, and it’s thought that many cases go undiagnosed. An estimate, however, may be made based on the incidence of heat-related events.
Among those who develop heat-related injuries (such as heat exhaustion or heat stroke), the incidence is substantial. It was noted that among soldiers who developed heat-related illness, 31% had hypohidrosis.
Symptoms and Complications
Most of the time, reduced sweating goes largely unnoticed unless a person suffers a heat-related illness.
Symptoms of a lack of sweating may include:
- Feeling hot or overheated
- Difficulty or an inability to cool down after becoming overheated
- Heat “intolerance”
- Muscle cramps in the arms, legs, abdomen, or back, often lasting for a significant period of time
- Tingling pain in the extremities
Complications of a lack of sweating (hypohidrosis or anhidrosis) are the most common reason why a person will seek medical treatment and receive a diagnosis. Children, as well as older adults, are at greater risk of these complications that include:
- Heat rashes: Resembling pimples, rashes related to heat exposure are most common near folds of the skin, such as on the neck, elbow creases, and groin.
- Heat cramps: Not a specific diagnosis, heat cramps may be the first sign that further complications may occur.
- Heat exhaustion: Heat exhaustion is often characterized by skin that is cold, pale, and clammy and accompanied by profuse sweating. Heart rate may be elevated along with a weak pulse, and symptoms such as muscle cramps, nausea, and lightheadedness are often present.
- Heat stroke: Heat stroke is a medical emergency characterized by a body temperature of 103.0 F or greater. The skin is often hot and red. Heart rate is often rapid and feels strong rather than weak. Headaches may be present, and lightheadedness may progress to loss of consciousness.
While complications such as these are more common in those who have hypohidrosis or anhidrosis, they may occur in people who sweat normally, and it’s important for everyone to be aware of the symptoms.
A lack of sweating can predispose people to heat cramps, heat exhaustion, and heat stroke, a medical emergency.
There are many potential causes for a reduction or absence of sweating, including both congenital and acquired conditions. In some cases, a lack of sweating arises for unknown reasons, which is called “idiopathic.”
Acquired conditions may be either primary, or secondary (due to other diseases) such as conditions that affect the skin and sweat gland directly, connective tissue diseases, medications, and central or peripheral nervous system conditions that affect the communication between the brain and the sweat glands.
A number of congenital/genetic conditions have been associated with either hypohidrosis or anhidrosis. These include:
- Hypohidrotic ectodermal dysplasia
- Congenital insensitivity to pain and anhidrosis
- Fabry disease (a condition that affects both sweat glands and metabolism)
- Congenital absence of sweat glands
- Ross syndrome
The gene ITPR2 codes for a receptor within the cell that is primarily responsible for the production of sweat by the sweat glands.
In addition to congenital conditions leading to a reduction or absence in sweat glands, a number of skin conditions may affect the sweat glands or cause of occlusion of the glands, and hence, sweat production. Examples include:
- Skin damage due to radiation
- Leprosy (leprosy can also cause peripheral neuropathy, see below)
Central Nervous System Conditions
Conditions involving either the central nervous system or peripheral nervous system are common causes of a lack of sweating. The term autonomic function describes processes by which the body controls homeostasis in the body at an unconscious level, and a number of conditions can lead to an impairment in the autonomic nervous system.
This is easier to understand by picturing the control of sweating. Signaling begins in the hypothalamus with central pathways leading first to the brainstem and then to the spinal cord. From the spinal cord, nerves travel via peripheral nerves, sympathetic chain ganglia, etc., before arriving at the sweat glands.
Medical conditions affecting structures at any point in this pathway may result in a lack of sweating.
Some central nervous system conditions associated with reduced or absent sweating include:
- Multiple system atrophy
- Parkinson’s disease
- Dementia with Lewy bodies
- Multiple sclerosis
- Shy–Drager syndrome
Spinal cord injuries are also a potential cause of lack of sweating. With these injuries, there is usually a band of excess sweating (hyperhidrosis) above the level of the injury and anhidrosis below.
Peripheral Nervous System Conditions
Conditions involving the peripheral nervous system may also be responsible for a lack of sweating. Some peripheral nervous system conditions associated with problems in sweating include:
- Pure autonomic failure
- Harlequin disease
- Guillain-Barre syndrome
Peripheral neuropathy, or damage to nerves found between the spinal cord and the sweat glands that may result in a lack of sweating. There are a number of conditions that can result in peripheral neuropathy including:
- Diabetic peripheral neuropathy
- Alcoholic peripheral neuropathy
- Amyloid neuropathy
- Neuropathy due to leprosy
- Paraneoplastic neuropathy
Connective Tissue/Autoimmune Disorders
Sweat glands may not work properly in a number of connective tissue diseases, for example, Sjogren’s syndrome, lupus, scleroderma, and progressive systemic sclerosis. There are several mechanisms involved that may involve both skin conditions and peripheral nervous system dysfunction.
A number of different medications can lead to a reduction or absence of sweating, in many cases, related to their effects on acetylcholine, the primary neurotransmitter involved in signaling pathways between the brain and sweat glands. Some of these include:
- Anticholinergics: Anticholinergic medications interfere with the signals from the break to the sweat glands that result in sweating. Examples include Lomotil (atropine), belladonna, Robinul (glycopyrrolate), Levsin (hyoscyamine), and Symmetrel (amantadine).
- Antidepressants, especially tricyclic antidepressants such as Elavil (amitriptyline), Anafranil (clomipramine), Norpramin (desipramine), Sinequan (doxepin), Pamelor (nortriptyline), and Tofranil (imipramine)
- Anti-epilepsy drugs such as Topamax (topiramate), Zonegran (zonisamide), and Tegretol (carbamazepine)
- Opioid medications, such as morphine (these medications raise the setpoint for temperature in the hypothalamus)
- Antipsychotics such as Clozaril (clozapine) and Zyprexa (olanzapine)
- Muscle relaxants such as Flexeril (cyclobenzaprine)
- Oxybutynin (used for bladder spasms or excess sweating)
- Calcium channel blockers such as Procardia (nifedipine)
- Anti-vertigo drugs such as scopolamine
- The chemotherapy drug 5-fluorouracil
There are several other causes that don’t fall neatly into the categories above. Some of these include the following:
Small cell lung cancer, a type of lung cancer that accounts for roughly 15% of lung tumors may cause anhidrosis as a type of paraneoplastic syndrome. In this case, a complete lack of sweating may occur on one side of the body with excess sweating (hyperhidrosis) on the other side.
Anhidrosis may also be seen with non-small cell lung cancers that grow near the top of the lungs (Pancoast tumors). In this case, a lack of sweating is often accompanied by droopy eyelids (ptosis) and constricted pupils (miosis).
Graft vs. Host Disease
Graft vs. host disease is a complication of bone marrow/stem cell transplants in which the donor cells attack the host (the person receiving the transplant).
Silicone Breast Implants
Uncommonly, chronic silicone exposure such as in the case of silicone breast implants may lead to a lack of sweating. In this case, it’s thought that inflammation (autoimmune) directly affects the sweat glands.
Idiopathic acquired anhidrosis has no obvious cause. It is broken down into three types based on where the problem occurs.
- Idiopathic generalized anhidrosis is considered a type of neuropathy (peripheral nervous system) condition
- Idiopathic segmental anhidrosis occurs higher up in the nervous system (sudomotor failure)
- Ross syndrome occurs at the level of the sweat gland.
Acquired idiopathic generalized anhidrosis (AIGA) most often occurs in young adults (especially males) who have no underlying health conditions. The most common symptoms include itching and a prickly type of pain sensation whenever the body reaches a temperature where sweating occurs (even an elevation of less than 1 degree F).
Due to the very uncomfortable sensation, many of these people see their doctor with concerns that they are unable to exercise. Sometimes a rash occurs along with the other symptoms, but symptoms tend to resolve rapidly when the body cools down.
Roughly half of the people also have a condition in which hives occur as a response to stress or other precipitating factors (cholinergic urticaria). With AIGA, people are quire susceptible to heatstroke. Oral corticosteroids appear to be quite effective for many people, though the condition frequently recurs.
The diagnosis of a lack of sweating begins with having a high index of suspicion and can be challenging in many cases. Testing usually begins with confirming a lack or reduction in sweating as well as a search for underlying causes when these are not known or obvious.
History and Physical
A careful history and physical, especially with regard to neurological symptoms or heat-related injuries is important. A family history may be helpful in some cases. Certainly, a careful review of medications is essential.
On exam, neurological findings (either central or peripheral) may be present. Unfortunately, it can be difficult to confirm a lack of sweating in a comfortable exam room, and further testing is needed.
There are a number of different tests that may be done to confirm a reduction or absence of sweating. It is important that medications such as anticholinergics be discontinued before testing is performed. Testing options include:
- Thermoregulatory sweat test: This is one of the easiest tests to diagnose anhidrosis.
- Sympathetic skin response: This test measures the electrical potential in the skin
- Silastic sweat imprint test: With this test, pilocarpine is given to stimulate sweat glands and electrodes applied to stimulate the skin. As sweating occurs, the sweat droplets cause an impression on the silastic material.
- Quantitative sudomotor axon reflex test (QSART): With this test, acetylcholine and electrodes are used to stimulate the skin and sweat glands. In this case, the sweat droplets are collected and measured quantitatively.
With connective tissue/autoimmune conditions, blood tests may be helpful in characterizing the diagnosis.
If a hereditary cause (such as ectodermal dysplasia) is suspected, genetic testing may be recommended for confirmation.
Less commonly, a skin biopsy may be needed to evaluate the status of the sweat glands.
If a central nervous system or spinal cord disorder is suspected, imaging tests such as a computerized tomography (CT) scan or magnetic resonance imaging (MRI) may be recommended.
The treatment of hypohidrosis or anhidrosis begins with reducing the risk of complications and addressing the underlying cause when possible. Simply having an awareness of the condition and being able to recognize the early symptoms of heat exhaustion and heatstroke can be very helpful.
Home remedies are the mainstay of treatment for the majority of people with hypohidrosis or anhidrosis. This includes avoiding situations that can result in complications, such as high temperatures outside and excess exercise as well as staying well hydrated. Moving slowly when you need to be outside in hot weather is also important.
If you begin to notice overheating, a number of measures may be helpful:
- Use a cool water or ice pack, especially when cooling is applied to areas such as the neck, forehead, armpits, and groin.
- If a rash is present, applying powder (like baby powder) may be soothing.
- Drink an electrolyte/sport drink if available, otherwise drink plenty of water.
Condition Based Treatment
When a medication is thought to be the culprit, changing to a medication in a different category (one that doesn’t affect acetylcholine) may be an option. Immunosuppressive medications may be needed for autoimmune/connective tissue disorders that are causing anhidrosis or hypohidrosis.
Acquired idiopathic hypohidrosis is thought to be greatly under-diagnosed. An appropriate workup is essential, as the risk of heat exhaustion and heat stroke is real, and treatment with high dose corticosteroids (oral or IV) can be very beneficial.
Treatment of Complications
Conservative measures may be enough for mild symptoms such as heat rash or heat cramps. Exceptions include those who have a history of a heart condition or who are eating a low sodium diet. In this case, medical care may be needed even without signs of heat exhaustion or heat stroke.
Heat exhaustion often responds to home remedies without the need for medical care. Using cool compresses, moving away from heat, and taking sips of water may help. Signs that indicate medical attention is needed include vomiting, symptoms that are worsening despite taking these measures, or those that last more than one hour.
Heatstroke is a medical emergency, and if you expect you may have heatstroke you should call 911 without hesitation.
While waiting, it is important to move yourself (or the person suspected of having heat stroke) to a cool place and begin applying cool compresses. Even though it is counterintuitive, you should avoid drinking or giving the person anything to drink while waiting for attention.
Coping and Prevention
Even if hypohidrosis/anhidrosis is unlikely to cause significant heat-related injuries, it can still seriously impact your quality of life.
An ounce of prevention is important with sweating disorders as with other conditions. If you are living with hypohidrosis or anhidrosis, avoid exercising out-of-doors when it’s hot, especially in hot, humid weather.
Indoors, use air conditioning to keep yourself comfortable. Stay well hydrated. Loose-fitting, lightweight clothing is usually most comfortable.
If you start becoming warm, move indoors if outside, and turn the air conditioning to a lower temperature if indoors. Having a spray bottle on hand may help you cool down quickly if you start to notice overheating. This is particularly helpful when applied to regions such as your armpits, groin, and neck.
Since a lack of sweating isn’t as recognized as a medical condition by much of the public, finding others who are coping with similar challenges can be priceless. There are a number of online communities for people coping with anhidrosis in general, as well as those for people coping with specific diagnoses such as acquired idiopathic hypohidrosis or hypohidrotic ectodermal dysplasia.
Since the conditions are relatively uncommon, pursuing online groups allows you to communicate with people anywhere in the world who are facing a similar condition.
A Word From Get Meds Info
A lack of sweating (hypohidrosis or anhidrosis) can range from mild to serious and has many potential underlying causes. Fortunately, having an awareness of your tendency to overheat, and quickly instituting at home remedies when needed may be all that’s needed to keep yourself healthy.