Eccrine vs. Apocrine vs. Apoeccrine Glands: What's Actually Different

“Sweat glands” sounds like a single thing. It isn’t. You have three distinct types, located in different places, producing different secretions, controlled by different mechanisms, and serving different purposes. Understanding them is actually interesting, and it explains a lot of things that otherwise seem mysterious.

Eccrine glands: the thermostat workers

Eccrine glands are the main act. You have somewhere between 2 and 4 million of them, distributed across virtually your entire skin surface. They’re most concentrated on:

• Palms, 600-700 per square centimeter
• Soles, similarly dense
• Forehead
• Cheeks

Eccrine glands are simple coiled tubular glands that extend from the dermis up through the epidermis and open directly at pores on the skin surface.

What do they produce? Mostly water, about 99% of eccrine sweat is water. The rest is sodium chloride (salt), potassium, trace amounts of urea and ammonia, and small amounts of other solutes. When it evaporates from your skin surface, it carries heat with it. This is the core mechanism of human thermoregulation.

Eccrine sweating is triggered primarily by:

• Thermal stimulus, elevated core or skin temperature
• Exercise
• Fever
• Emotional stress (eccrine glands do respond to stress, particularly on the palms and soles, which is why “sweaty palms” happens with nervousness)

The sympathetic nervous system controls eccrine glands, but unusually, it uses acetylcholine as its neurotransmitter, not norepinephrine (adrenaline) as it does for most other sympathetic functions. This is why beta blockers (which block adrenaline effects) don’t fully treat hyperhidrosis, and why anticholinergic drugs like glycopyrrolate (which block acetylcholine) do work.

Apocrine glands: the stress and odor contributors

Apocrine glands are anatomically different and serve a different purpose. Key facts:

Location: Concentrated in the armpits (axilla), groin, around the nipples, the perianal area, and the ear canal (ceruminous glands are a variant). They’re not evenly distributed, they cluster in specific zones.

Structure: Larger than eccrine glands, with a secretory coil in the dermis that empties into a hair follicle, not directly onto the skin surface.

What they produce: A thicker, milky, protein-and-lipid-rich secretion. Fresh from the gland, this secretion is actually odorless. The characteristic smell develops when skin bacteria (particularly Staphylococcus and Corynebacterium species) break down the proteins and lipids in the secretion, releasing volatile fatty acids and thioalcohols that produce the characteristic body odor smell.

Trigger: Apocrine glands respond primarily to emotional and psychological stimuli, stress, fear, sexual arousal. They’re part of the flight-or-fight response. Exercise does not strongly activate apocrine glands.

This is why stress sweat smells different, and worse, than exercise sweat. Exercise sweat is mostly eccrine output: water and salt, which evaporates cleanly and doesn’t feed bacteria in the same way. Stress sweat activates apocrine glands and produces the odor-generating substrate.

Apocrine glands also produce pheromone-like compounds, the science here is still debated, but there’s reasonable evidence that apocrine secretions contain chemical signals that influence social and sexual behavior, though the human olfactory system is far less attuned to these than in other mammals.

Apoeccrine glands: the third type most people haven’t heard of

Apoeccrine glands were first formally described in 1987 and are still less widely known than the other two. They’re found exclusively in the axillary (armpit) region, developing from eccrine glands during puberty.

They share structural characteristics of both eccrine and apocrine glands, they have the larger secretory coil of apocrine glands but open directly on the skin surface like eccrine glands.

What they produce: a secretion somewhere between eccrine and apocrine, watery, but more protein-rich than pure eccrine sweat.

Why they matter for hyperhidrosis: Apoeccrine glands appear to be disproportionately active in people with axillary hyperhidrosis. Some research suggests they may contribute more to underarm sweating volume than traditional eccrine glands in affected individuals, which has implications for how treatments work.

How this relates to antiperspirant and treatment

Antiperspirants (aluminum-based) work on eccrine glands, they plug the eccrine duct opening, reducing sweat output. They work for thermal and emotional eccrine sweating.

Deodorants work on apocrine output, they either kill the bacteria that produce odor from apocrine secretions, or mask the smell, or both. They don’t reduce sweating volume.

This is why antiperspirant and deodorant are different products doing different things, even though they’re often combined in the same stick.

Botox for sweating blocks acetylcholine release at eccrine glands, it interrupts the signal that tells them to activate. This is why it’s effective for hyperhidrosis.

Anticholinergic medications (glycopyrrolate, oxybutynin) work systemically to block acetylcholine receptors throughout the body, reducing eccrine gland activity across the board, with the side effects that come from blocking acetylcholine everywhere else too.

MiraDry destroys both eccrine and apoeccrine glands in the underarm area using microwave energy, permanent reduction because the glands don’t regenerate.

The anatomy explains the geography of sweating

Once you understand the distribution of sweat glands, a lot of things make more sense:

• Why hands and feet sweat so much under stress: Palmar and plantar eccrine gland density is extremely high, and these areas have a strong emotional response component built into their neural control.
• Why armpit sweat smells and hand sweat doesn’t: Armpits have apocrine glands. Hands have mostly eccrine glands.
• Why certain people develop hyperhidrosis only in specific areas: The eccrine distribution and neural control pathways are zone-specific, the signaling dysfunction tends to be localized.
• Why antiperspirant works on armpits but doesn’t fix sweaty palms: The density and type of glands in the palms makes aluminum-based plugging much less effective there.

Understanding the plumbing makes the treatments make more sense, and helps you ask better questions when you’re looking for a solution.

Sweat Glands Across the Lifespan

Sweat gland activity is not static. It changes significantly from birth through old age, and those changes explain a lot about why sweating patterns shift as you get older.

At birth and early childhood: Newborns have all their sweat glands already formed, but eccrine glands are not fully functional at birth. Full thermoregulatory sweating capacity develops over the first two to three years of life. Young children sweat less efficiently than adults, which is one reason they’re more vulnerable to heat illness.

Puberty: This is when apocrine glands activate. Before puberty, apocrine glands exist but are essentially dormant. The hormonal surge of puberty (primarily androgen activity) triggers apocrine glands to become functional. This is the direct cause of body odor emerging in adolescence: the apocrine secretions become available for bacteria to metabolize for the first time.

This is also why teenage body odor is often more intense than adult body odor. Freshly activated apocrine glands combined with active bacterial colonization, in an adolescent who may not yet have an effective hygiene routine, produces the characteristic result. It’s not a character flaw. It’s biology running on schedule.

Adulthood: Eccrine gland output is at its highest in the twenties and thirties. This is when primary hyperhidrosis is most commonly diagnosed and most actively problematic. Apocrine glands are fully active throughout adulthood.

Older adulthood: Eccrine gland output decreases with age. Both the number of active eccrine glands and their output per gland tend to decline from middle age onward. Older adults genuinely sweat less in absolute volume than younger adults under the same conditions.

This has practical consequences. Heat tolerance decreases in older adults partly because sweating, the primary cooling mechanism, is less efficient. Older adults are at higher risk of heat exhaustion and heat stroke in hot conditions for this reason.

For people managing hyperhidrosis, there’s a practical implication: sweating severity tends to decrease somewhat with age for people with primary hyperhidrosis. Many people in their fifties and sixties report that the condition has become less severe than it was in their twenties and thirties. Treatment needs may evolve over time rather than remaining static.

What Hyperhidrosis Actually Does to Sweat Gland Activity

The most common misconception about hyperhidrosis is that people who have it have more sweat glands than average. This is not accurate. Gland count is not the issue.

Research on primary hyperhidrosis consistently shows that the sweat glands themselves are structurally normal. The number of glands is not elevated. The glands are not enlarged or structurally abnormal. When examined under a microscope, a hyperhidrotic sweat gland looks the same as a normal one.

What is abnormal is the nervous system signaling. The sympathetic nerve fibers that control eccrine gland activation are firing more frequently, more intensely, or in response to lower-threshold stimuli than they would in someone without hyperhidrosis. The glands are functioning correctly; they’re just receiving too many activation signals.

This is why the condition is sometimes described as a “misfiring thermostat.” The hardware (the glands) is fine. The control signal (the sympathetic nerve activity) is calibrated wrong.

At the cellular level, each sweating episode in hyperhidrosis looks like normal sweating. The eccrine gland receives acetylcholine from the sympathetic nerve ending, responds by secreting fluid, and that fluid exits through the duct. The mechanism is identical to normal sweating. The difference is how often and how strongly that signal arrives.

This also explains why anticholinergic treatments work. Glycopyrrolate, oxybutynin, and Qbrexza all work by blocking acetylcholine receptors, interrupting the signal before it can tell the gland to produce sweat. The gland is ready and willing; the treatment simply prevents the order from arriving.

Botox works one step earlier: it prevents the nerve ending from releasing acetylcholine in the first place. The signal never even reaches the gland. Both approaches address the signaling problem rather than the gland itself, because the gland isn’t the problem.

Sources

1. A New Eccrine Sweat Gland (Apoeccrine Gland), First Description, Journal of Investigative Dermatology, 1987 (foundational apoeccrine gland paper)
2. Eccrine Sweat Glands: Anatomy, Physiology, and Pathophysiology, StatPearls / NCBI Bookshelf, 2023
3. Acetylcholine as the Neurotransmitter of Eccrine Sweat Glands, Journal of the American Academy of Dermatology, 2004
4. Sweat Gland Structure and Function, Skin Appendage Disorders, 2018
5. Apocrine and Eccrine Gland Biology, Journal of Investigative Dermatology Symposium Proceedings, 2011