What Is the Difference Between Eccrine and Apocrine Glands?

Humans have two main types of sweat glands, eccrine and apocrine, and they differ in almost every way that matters: where they sit, what they produce, when they become active, and what they’re actually for. Eccrine glands blanket most of your body and handle temperature control by releasing a watery, mostly odorless sweat. Apocrine glands cluster in a few specific zones, produce a thicker secretion loaded with fats and proteins, and are far more involved in the chemistry behind body odor than most people realize. There is also a lesser-known third type, the apoeccrine gland, that blurs the line between the two and complicates the tidy binary.

Where Each Type Lives

Eccrine glands are everywhere. They open directly onto the skin surface and show up across nearly the entire body, with the densest concentrations on your palms and the soles of your feet. Apocrine glands, by contrast, occupy a much more limited territory: the armpits, the groin, the area around the nipples, and the ear canals.¹ That distribution matters. Apocrine glands almost always empty into hair follicles rather than directly onto the skin, which is why the areas they occupy tend to be hairy. Eccrine glands skip the follicle entirely and open through their own tiny pores.

This difference in location explains something practical. When people worry about excessive sweating on their hands or forehead, the problem is eccrine-driven. When people worry about underarm smell, the apocrine glands are almost always part of the story, even though eccrine glands are also present in the armpit.

How They Secrete and What Comes Out

The two gland types don’t just differ in location; they use fundamentally different mechanisms to get their product out. Eccrine glands secrete only liquid from the cell interior, pushing out a dilute, watery fluid that is mostly salt water. Apocrine glands use a more destructive process: they pinch off the outer part of the cell, releasing chunks of cellular material along with the fluid. Because cell contents come along for the ride, hydrophobic substances like lipid derivatives end up in the secretion, and the result is not diluted the way eccrine sweat is.²

The practical upshot: eccrine sweat is thin, clear, and salty. Apocrine sweat is viscous, milky, and rich in lipids, proteins, sugars, and ammonia.³ Fresh apocrine secretion is actually odorless, which surprises people. The smell comes later, once skin bacteria get to work on it.

Why Body Odor Is Really a Bacteria Problem

The widespread belief that sweat itself stinks is only half right, and only for a specific reason. Body odor is primarily created when bacteria living on the skin break down the odorless components of sweat into volatile, smelly compounds. The key players are Staphylococcus species and Corynebacterium species. Staphylococcus hominis and Staphylococcus epidermidis, for example, can independently produce malodor by converting fatty acids and amino acids in sweat into acetic acid, isovaleric acid, and sulfur-containing compounds.⁴

Corynebacterium species add to the picture. Research into their genomes has confirmed that the major odor-causing substances in human sweat include steroid derivatives, short branched-chain fatty acids, and sulphanylalkanols, all produced through bacterial transformation of originally odorless precursors.⁵ Apocrine sweat provides the richest buffet for these bacteria because of its high lipid and protein content. That’s why underarm odor tends to be stronger than the smell from, say, a sweaty forehead, even though both regions are moist.

This bacterial connection is also why deodorants and antiperspirants take two different approaches. Deodorants target the bacteria with antimicrobial agents, trying to stop the smell at its microbial source. Antiperspirants reduce the flow of sweat itself, using aluminum salts that form a gel plug in the sweat pores and physically obstruct fluid from reaching the skin surface.⁶ Both approaches reduce odor, but they work on completely different parts of the process.

Puberty as the Turning Point

Eccrine glands are functional from birth. Apocrine glands are not. They sit dormant through childhood and only begin secreting once sex hormones surge at puberty. This is why young children can sweat profusely but rarely have noticeable body odor: the glands responsible for producing the bacterial fuel are still inactive.

The hormonal activation is direct. Apocrine gland cells in the armpit contain androgen receptors and estrogen receptors. Research using immunofluorescence staining has shown strong nuclear reactivity for androgen receptors in the secretory lining of these glands, and the staining intensity correlates with the height of the epithelium, with taller, more active secretory segments showing more intense receptor expression.⁷ In other words, the glands aren’t just switched on by hormones in a general sense; they have built-in receptors that link secretory activity tightly to circulating steroid levels.

The Third Type You Probably Haven’t Heard Of

The eccrine-versus-apocrine binary, while useful, isn’t complete. In the late 1980s, researchers described a third category of sweat gland found only in the human armpit: the apoeccrine gland. These glands develop during puberty from pre-existing eccrine glands, typically between the ages of about 8 and 14. By the late teens, apoeccrine glands can make up as much as 45% of all axillary sweat glands.⁸

What makes them interesting is that they look partly like apocrine glands under a microscope, with similar dilated segments, but they behave more like supercharged eccrine glands. They produce copious amounts of clear, salty fluid rather than the thick secretion typical of apocrine glands. In lab testing, the average sweat output of a single apoeccrine gland over a 30-minute period was sevenfold higher than that of a regular eccrine gland.⁹ They also show higher sensitivity to the neurotransmitter that drives sweating. So if you’ve ever noticed that your armpits seem to produce a disproportionate amount of liquid sweat compared to other body parts, apoeccrine glands are likely contributing.

Apoeccrine glands are consistently present in adult armpits regardless of sex or race, but they are absent in children under about six years old. Their discovery complicated earlier research that tried to explain armpit sweating purely in terms of eccrine and apocrine function.

Thermal Sweating Versus Emotional Sweating

Not all sweating responds to the same trigger, and the two gland types are wired differently. Eccrine glands across most of your body are activated by heat and controlled through cholinergic nerve signals. When your core temperature rises, the brain sends signals that cause eccrine glands to pump out sweat, which evaporates and cools the skin.

But eccrine glands on the palms and soles follow a different rule. They do not usually respond to heat. Instead, they are activated by emotional stimuli: stress, anxiety, mental effort, or even deep breathing. This “emotional sweating” serves a grip-enhancing function, helping to prevent slippage during tasks requiring fine motor control or while grasping objects.¹⁰ Anyone who has noticed sweaty palms before a job interview or while watching a tense movie has experienced this system in action. It’s the same gland type doing something completely different depending on where it sits.

Apocrine glands, meanwhile, respond strongly to emotional stimuli and sympathetic nervous system activation through adrenergic innervation but do not respond to cholinergic or thermal stimulation the way eccrine glands do. This means apocrine glands don’t participate meaningfully in cooling you down. Their secretion is triggered by stress, fear, or arousal rather than by exercise or a hot room.

Modified Apocrine Glands in Unexpected Places

Apocrine glands have evolutionary cousins in some specialized locations. The ceruminous glands in the ear canal, for example, are modified apocrine glands. They use the same pinching-off secretion mechanism, in which actin filaments and specific cytokeratins help sever the top portion of the cell, releasing its contents. These glands work together with sebaceous glands to produce cerumen, better known as earwax.¹¹ The mammary glands that produce breast milk are also considered modified apocrine glands, sharing the same general secretory lineage. So the apocrine mechanism isn’t limited to body odor; it has been co-opted for very different purposes across different parts of the body.

Why Humans Sweat So Much More Than Other Primates

The eccrine gland is one of the defining features of human biology. Humans have roughly ten times the eccrine gland density of chimpanzees and macaques across virtually all body regions.¹² That enormous density, combined with our relative lack of body hair, gives us a thermoregulatory capacity that is extreme among mammals.

This capacity was almost certainly shaped by natural selection. Evidence from comparative primate studies suggests that species living in hot, dry climates with eccrine glands on the body surface were selected for increased sweating ability, likely involving enhanced glycogen content in sweat gland cells and better blood supply to the glands.¹³ The result was a cooling system powerful enough to support sustained physical activity under the open sun, something few other large mammals can do. Long-distance running in equatorial heat, the kind of endurance hunting that likely characterized early human subsistence, depends on the eccrine system.¹⁴

Apocrine glands tell a different evolutionary story. In many mammals, apocrine-type glands are the primary sweat gland and are distributed much more widely. Humans appear to have traded broad apocrine coverage for dense eccrine coverage, retaining apocrine glands only in areas where their chemical signaling function, rather than their cooling function, still mattered.

How Sweat Glands Change with Age

Both gland types change over a lifetime, but the eccrine system’s decline has the most practical consequences. Structural studies of skin from younger and older adults have found that while the density and volume of eccrine sweat glands don’t actually change with aging, the glands shift closer to the skin surface. This happens because the dermis thins with age, and the secretory ducts become more tortuous and meandering even though their length stays the same.¹⁵

Functionally, the decline is more dramatic. Forearm sweat rate drops measurably starting in middle age for men and somewhat later for women. In men, the decline is driven by reduced output per gland; in women, it involves both reduced output and a drop in gland density.¹⁶ This age-related reduction in sweating capacity is one reason older adults are more vulnerable to heat-related illness. The cooling system that served them well at 30 doesn’t perform the same at 70.

Sweat as an Immune Defense

Eccrine sweat does more than cool you off. It carries antimicrobial peptides that form part of the skin’s innate immune defense. The most studied of these is dermcidin, a peptide constitutively secreted by eccrine glands. Its discovery demonstrated that sweat actively participates in defending the skin against infection, not just passively by washing microbes away, but by delivering molecules that kill pathogens on contact.¹⁷ This defense is continuous, meaning every time you sweat, you’re coating your skin with a thin layer of antimicrobial protection. It’s one of the underappreciated fringe benefits of having such a dense eccrine system.

When Things Go Wrong

The two gland types are involved in different clinical problems. Primary hyperhidrosis, or excessive sweating that isn’t caused by another medical condition, is an eccrine gland disorder. It results from overactivation of the sympathetic nervous system, leading to far more sweat production than the body needs for cooling.¹⁸ Recent cell-culture research has identified specific molecular players: a water channel protein called aquaporin 5 and a transport protein called NKCC1 are both overexpressed in sweat glands from patients with primary hyperhidrosis, and their expression levels are positively correlated, suggesting they work together in driving the excess fluid production.¹⁹

On the apocrine side, the most talked-about disorder is hidradenitis suppurativa, a painful chronic skin condition that produces abscesses and scarring in areas rich in apocrine glands, especially the armpits and groin. Despite a longstanding assumption that excessive sweating plays a role, gravimetric testing of patients has shown that hidradenitis suppurativa is not actually associated with hyperhidrosis. Instead, the apocrine glands in affected skin show a proinflammatory signature, with elevated levels of inflammatory signaling molecules in the sweat itself.²⁰ This finding is shifting how researchers think about the disease: it may be less about sweat blockage and more about the apocrine glands actively contributing to inflammation.

Sweat as a Diagnostic Fluid

The chemical differences between eccrine and apocrine sweat have caught the attention of biomedical engineers working on wearable health sensors. Because eccrine sweat is dilute and salty, flowing through individual pores all over the body, it’s an attractive target for non-invasive monitoring. Wearable biosensors placed on the skin can collect eccrine sweat and measure analytes like glucose, lactate, sodium, and cortisol in real time. The goal is continuous health data without a blood draw.

The challenge is that apocrine and eccrine glands respond to different stimuli. Eccrine glands fire in response to heat and cholinergic stimulation, while apocrine glands respond to emotional arousal and adrenergic stimulation but not to heat. If a sensor is placed on an area where both gland types are active, like the armpit, the mixed secretion complicates interpretation. Most wearable sensor designs focus on eccrine-rich areas like the forearm or forehead precisely because the sweat there is more chemically consistent and predictable. Understanding which gland type dominates a particular skin region turns out to be essential for accurate biosensor design.