Anhidrosis, the partial or complete inability to sweat, strips the body of its primary cooling system and can turn ordinary warm weather into a medical emergency. The condition ranges from small patches of skin that stay dry to a near-total absence of perspiration, and it stems from a surprisingly diverse set of causes: inherited genetic syndromes, nerve damage, autoimmune attack on sweat glands, and even common medications. Because sweating is something most people never think about until it stops working, anhidrosis often goes unrecognized until someone collapses from overheating.
How Sweating Normally Works
Your body has between two and four million eccrine sweat glands distributed across nearly every square centimeter of skin, with the highest concentrations on the palms, soles, and forehead. When your core temperature rises, the brain’s thermoregulatory center sends signals down sympathetic nerve fibers that release the chemical messenger acetylcholine. That acetylcholine binds to receptors on the sweat gland, triggering a cascade that pulls sodium, potassium, and chloride into the gland’s secretory coil, dragging water along with them.1PubMed Central. Physiology of sweat gland function: The roles of sweating and sweat composition in human health The resulting fluid rises through a duct to the skin’s surface, where it evaporates and carries heat away. Recent live-imaging work has shown that tiny muscle-like cells wrapped around the coiled duct contract in a peristaltic wave to pump sweat upward, a bit like squeezing toothpaste from a tube.2PubMed Central. Gap junction-mediated contraction of myoepithelial cells induces the peristaltic transport of sweat in human eccrine glands
This system is remarkably effective. A healthy adult can produce over a liter of sweat per hour during vigorous exercise in the heat, making humans among the most prolific sweaters in the animal kingdom. The eccrine sweat gland is considered central to the evolution of our species, because it allowed early humans to stay active in open, hot environments where other large mammals had to rest.3PubMed. Diversity and evolution of human eccrine sweat gland density Anything that disrupts the nerve signal, the gland itself, or the chemical handoff between them can produce anhidrosis.
Genetic Causes
Some people are born with sweat glands that never formed properly. The most common inherited cause is hypohidrotic ectodermal dysplasia (HED), a group of genetic conditions that affect the development of structures derived from the outer embryonic layer: hair, teeth, nails, and sweat glands. The X-linked form accounts for the majority of cases and results from mutations in the gene for ectodysplasin, a signaling protein that tells the developing fetus to build these structures.4PubMed. Hypohidrotic ectodermal dysplasia: clinical and molecular review Boys with this form often have sparse hair, missing or peg-shaped teeth, and greatly reduced numbers of sweat glands. Because the gene sits on the X chromosome, girls who carry one copy of the mutation usually have milder symptoms, though some have patchy areas of reduced sweating.
A rarer and more dramatic genetic condition is congenital insensitivity to pain with anhidrosis, or CIPA. This disorder results from mutations in the NTRK1 gene, which encodes a receptor critical for the development of sensory and sympathetic nerve cells. Without that receptor, the nerves that carry pain signals and the nerves that tell sweat glands to activate simply never develop properly.5PubMed Central. Congenital insensitivity to pain with anhidrosis: a literature review and the advocacy for stem cell therapeutic interventions Children with CIPA cannot feel pain, which leads to repeated injuries, and they cannot sweat, which makes fevers dangerously hard to control. It is exceedingly rare, but it illustrates how tightly linked the sweating and sensory nerve systems are.
Nerve Damage and Small Fiber Neuropathy
The nerve fibers that control sweating are among the thinnest in the body, classified as unmyelinated C fibers. That makes them especially vulnerable to damage from diabetes, alcohol use, and a range of autoimmune and metabolic conditions. When these small fibers degenerate, the result is small fiber neuropathy, and one of its earliest and most reliably detectable signs is reduced sweating.
In studies of patients with distal small fiber neuropathy, sweat testing picked up abnormalities in the vast majority of cases. One study found that sweat testing was abnormal in 90% of patients, with the pattern typically starting at the feet and working upward, mirroring the “stocking” distribution familiar from diabetic nerve damage.6PubMed. Distal small fiber neuropathy: results of tests of sweating and autonomic cardiovascular reflexes A larger follow-up study confirmed this, finding that 98% of patients with small fiber neuropathy showed sweat-related abnormalities on standardized testing, and the sweating deficit was far more common than problems with heart rate or blood pressure regulation.7PubMed. Detection of small-fiber neuropathy by sudomotor testing In other words, sweat glands are often the canary in the coal mine for small fiber nerve disease. If your feet have mysteriously stopped sweating while the rest of you drips normally, that asymmetry itself is a clue worth bringing to a doctor.
This pattern of nerve-driven anhidrosis also appears in conditions you might not expect. Recent research on hypermobile Ehlers-Danlos syndrome, a connective tissue disorder mainly known for joint flexibility and pain, found that patients had significant loss of autonomic nerve fibers in the skin, even more so than patients with idiopathic small fiber neuropathy.8PubMed. Distinct sensory and autonomic involvement in hypermobile Ehlers-Danlos syndrome compared with idiopathic small fiber neuropathy: a multimodal study The connection between connective tissue disorders and sweating dysfunction is an area where the evidence is still thin, but it is gaining attention.
Autoimmune Causes
The immune system can attack sweat glands directly, and Sjögren’s syndrome is probably the best-known example. Sjögren’s is classically associated with dry eyes and dry mouth, but the same immune assault that targets tear glands and salivary glands also hits eccrine sweat glands. Research has shown statistically significant reductions in sweat volume in people with Sjögren’s, with younger patients showing especially impaired sweating compared to healthy controls.9PubMed. Impaired sweating as an exocrine manifestation in Sjögren’s syndrome The proposed mechanisms include direct inflammatory destruction of gland tissue, autoantibodies that block acetylcholine’s action on the gland, and disruption of the sympathetic nerves that supply it.10PubMed Central. Acquired anhidrosis in a patient with Sjogren syndrome and silicone breast implants
Then there is a more puzzling entity called acquired idiopathic generalized anhidrosis, or AIGA. The name itself reveals the problem: “idiopathic” means the cause is unknown. People with AIGA suddenly lose the ability to sweat across most of their body, without an identifiable neurological, dermatological, or metabolic explanation. Biopsies often reveal clusters of immune cells, particularly T cells, surrounding the sweat glands, along with decreased expression of the acetylcholine receptor that triggers sweating.11PubMed Central. Acquired Idiopathic Generalized Anhidrosis (AIGA) and Its Complications: Implications for AIGA as an Autoimmune Disease AIGA predominantly affects young, physically active men, a demographic that depends heavily on intact thermoregulation. Military personnel and athletes are at particular risk because the condition can appear suddenly during a period of high physical demand.12PubMed. Early Recognition and Successful Treatment of Acquired Idiopathic Generalized Anhidrosis in a Deployed Servicemember
Medications That Shut Down Sweating
A number of widely prescribed drugs reduce sweating as a side effect, and this deserves more attention than it typically gets. The broad categories include anticholinergic medications, which block the same acetylcholine signal that triggers sweat glands; carbonic anhydrase inhibitors, which interfere with enzymes within the sweat gland itself; and tricyclic antidepressants.13PubMed. Drug-induced hyperhidrosis and hypohidrosis: incidence, prevention and management
Topiramate, used for epilepsy and migraine prevention, deserves special mention. In a pilot study of children and young adults on topiramate, the majority showed reduced sweat production on standardized testing. One child’s sweat output measured just 5% of the age-matched control level, and the deficit reversed when the drug was stopped.14PubMed. Oligohydrosis and hyperthermia: pilot study of a novel topiramate adverse effect The mechanism is thought to involve inhibition of carbonic anhydrase enzymes located within the sweat gland.15PubMed. Hypohidrosis during topiramate treatment: a rare and reversible side effect This is clinically important because children on topiramate who play sports or spend time outdoors in summer may overheat without anyone realizing why. Parents and prescribers rarely think to ask about sweating patterns.
The anticholinergic category is broader than many people realize. It includes not just drugs prescribed specifically for their anticholinergic effects, like oxybutynin for overactive bladder, but also older antihistamines, some antipsychotics, and certain anti-nausea medications. When an elderly person taking several of these drugs at once develops heat intolerance during a summer heat wave, the medication list is often the last thing anyone checks.
Compensatory Hyperhidrosis
Here is something counterintuitive: many people with anhidrosis sweat too much. When one region of the body loses its ability to sweat, the brain compensates by driving the remaining functional glands harder. The result is drenching sweat in the areas that still work, even though other areas remain completely dry.16PubMed. Sweating Disorders Someone with small fiber neuropathy affecting the legs, for example, might notice that their torso and face become much sweatier than before the neuropathy developed. This compensatory mechanism partially preserves the body’s overall cooling capacity, but it is imperfect, since the areas that cannot sweat are still at risk of local overheating, and the redistribution feels unpleasant and conspicuous.
This pattern also complicates diagnosis. A patient might come to a doctor complaining about excessive sweating on the face or trunk, and the conversation might focus entirely on hyperhidrosis, while the actual underlying problem is anhidrosis elsewhere on the body. Whole-body sweat mapping, rather than evaluating individual regions in isolation, is the clearest way to catch this.
How Anhidrosis Is Diagnosed
Diagnosing anhidrosis usually starts with a clinical suspicion: someone who overheats easily, develops unexplained fevers during exercise, or notices dry skin in areas that should be damp. From there, specialized sweat tests can map and quantify the deficit.
The thermoregulatory sweat test, or TST, is the gold standard for visualizing the problem. The patient is coated in an indicator powder that changes color when it contacts moisture, then placed in a heated chamber. After sweating is triggered, the areas that fail to change color show up as dry patches against a background of normal perspiration. TST provides a full-body map and can detect even subtle abnormalities at the tips of the toes. It evaluates the entire sweating pathway from the brain through the spinal cord to the nerve to the gland.17PubMed Central. Sweat testing to evaluate autonomic function
A complementary test called the quantitative sudomotor axon reflex test, or QSART, uses a small electrical stimulus and a dose of acetylcholine applied to the skin to activate only the final nerve segment and the gland itself. By comparing results from TST and QSART, doctors can often pinpoint whether the problem lies in the brain and spinal cord (preganglionic) or in the peripheral nerve and gland (postganglionic). TST tends to be more sensitive than QSART because it images the entire body rather than sampling just a few sites. In one study, TST detected sweating abnormalities in patients that QSART missed entirely.18JAMA Dermatology. Thermoregulatory Sweat Testing in Patients With Erythromelalgia
When the clinical picture suggests nerve damage, a skin biopsy can add another layer of information. Small samples of skin are taken and stained to visualize the nerve fibers threading through the epidermis and around the sweat glands. Reduced density of these fibers confirms neuropathic involvement and can sometimes correlate with the pattern seen on sweat testing.19PubMed. Quantification of sweat gland volume and innervation in neuropathy: Correlation with thermoregulatory sweat testing
The Danger of Overheating
Sweat is not optional equipment. It is the body’s dominant cooling mechanism, and when it fails, core temperature can rise rapidly to dangerous levels. Heat exhaustion, the milder stage, produces nausea, dizziness, heavy fatigue, and a sense of being unable to cool down. Heat stroke, the severe stage, is a medical emergency in which the core temperature exceeds about 40 °C (104 °F) and the brain begins to malfunction, producing confusion, seizures, and organ damage that can be fatal.
People with anhidrosis face this risk not just during extreme heat waves but during activities that a healthy person handles easily: a warm commute, a brisk walk on a sunny afternoon, sitting in a car with a broken air conditioner. Children with ectodermal dysplasia have historically been identified when they present with unexplained recurrent fevers, because nobody realized they could not sweat. As global temperatures climb, identifying people with impaired thermoregulation becomes increasingly relevant to public health.20PubMed Central. Global warming, heat-related illnesses, and the dermatologist
Living With Anhidrosis
There is no drug you can take to make absent sweat glands work, and when the nerve supply is irreversibly damaged, the deficit tends to be permanent. Management is almost entirely about external cooling and avoidance of situations where the body’s inability to self-cool could become dangerous.
Practical strategies include staying in air-conditioned environments during hot weather, wearing lightweight and loose-fitting clothing, carrying water and misting bottles, and scheduling physical activity for cooler parts of the day. Cooling vests, which use phase-change materials, evaporative fabrics, or air circulation, have been shown in systematic reviews to lower body temperature meaningfully in hot and humid conditions, making them a real option for people who need to work or exercise in the heat.21PubMed. The effect of cooling vests on physiological and perceptual responses: a systematic review For children with ectodermal dysplasia, schools often need to make accommodations: access to air conditioning, permission to leave outdoor activities, and awareness among staff that the child’s overheating is a medical issue and not a behavioral one.
The psychological burden should not be underestimated. Children and adolescents with ectodermal dysplasia deal with visible differences in hair, teeth, and facial features on top of the sweating deficit. A case report of a 15-year-old boy with the condition documented dramatic improvement in quality of life and confidence after a combination of reconstructive procedures and psychological counseling.22Europe PMC. Improvement in the Quality of Life of a Patient of Ectodermal Dysplasia with Reconstructive Surgeries The physical management is important, but so is addressing the isolation and self-consciousness that can accompany a condition most peers have never heard of.
When AIGA Can Be Treated
Among the acquired causes, AIGA stands out because it sometimes responds to immunosuppressive treatment, particularly when caught early. Because immune cells are often found clustered around the sweat glands on biopsy, corticosteroids and other immunosuppressants have been tried with varying success. A recent military case report described a deployed service member who was diagnosed with AIGA after sudden loss of sweating and severe heat intolerance. Biopsy confirmed the characteristic immune infiltrate around the sweat glands, and treatment led to recovery, underscoring the value of recognizing the condition before a heat casualty occurs.12PubMed. Early Recognition and Successful Treatment of Acquired Idiopathic Generalized Anhidrosis in a Deployed Servicemember Not all AIGA cases respond to treatment, and the long-term relapse rate is not well studied, but early intervention appears to improve the odds.
Prenatal Protein Replacement for Ectodermal Dysplasia
For most of its history, ectodermal dysplasia has been a condition you managed rather than treated. That may be changing. Researchers reasoned that since the X-linked form results from a missing signaling protein (ectodysplasin A1), providing a replacement version of that protein during fetal development, while sweat glands are still forming, might allow the glands to develop normally.
In an early clinical case, a recombinant version of the missing protein was injected into the amniotic fluid surrounding two affected twin fetuses and one affected singleton fetus. All three infants were born with the ability to sweat normally, and heat-related illness had not developed by the time of follow-up at 14 to 22 months of age.23PubMed. Prenatal Correction of X-Linked Hypohidrotic Ectodermal Dysplasia A subsequent expanded trial treated six boys prenatally with the same approach and reported that all six developed functional sweat glands. In the two oldest boys, normal sweating had persisted for more than five years.24PubMed Central. Ectodermal dysplasias: New perspectives on the treatment of so far immedicable genetic disorders
The numbers are still tiny, and the long-term durability beyond five years remains to be seen. But the principle is striking: a single prenatal intervention, timed during a narrow developmental window, appears to permanently correct the most dangerous feature of a genetic syndrome. It does not fix the dental or hair abnormalities, which develop on a different timeline, but the ability to sweat is the feature that poses the greatest immediate threat to life. If larger trials confirm these early results, prenatal protein replacement could become the first disease-modifying treatment for any form of ectodermal dysplasia.
Toxicological Causes
Environmental and occupational exposures can also damage sweat glands, though this is a less common route to anhidrosis. Thallium poisoning, once a favored method of criminal poisoning because of its delayed and initially vague symptoms, produces a distinctive dermatological pattern: hair loss, nail changes, and dry, rough skin accompanied by reduced or absent sweating. Older reports describe an initial period of heavy perspiration in the first days of poisoning, followed by the destruction of sweat glands and lasting anhidrosis.25Oxford Academic. Thallium distribution along segmented single hairs in a case of a criminal poisoning This two-phase pattern, sweating followed by its permanent loss, reflects the progressive destruction of the glandular tissue itself. Thallium poisoning is rare in everyday life, but it has appeared in forensic case reports and occupational settings involving certain industrial chemicals.
Other chemical exposures that can damage the autonomic nervous system or the sweat glands directly include certain heavy metals and industrial solvents, though individual case documentation for these is sparser. The broader point is that anhidrosis is sometimes the most visible sign of a systemic poisoning, and unexplained loss of sweating in a previously healthy person should prompt consideration of toxic exposures alongside the more common causes.