Men smell stronger than women primarily because of hormones. Testosterone drives the development of sweat glands that produce thicker, oil-rich secretions, and bacteria on the skin break those secretions down into pungent compounds. The result is a more intense body odor that kicks in at puberty and persists throughout adult life.
Testosterone Changes the Sweat Glands
Humans have two main types of sweat glands. Eccrine glands cover most of the body and produce watery, mostly odorless sweat for cooling. Apocrine glands cluster in the armpits, groin, and around the nipples, and they produce a thicker, lipid-rich fluid. That fluid is actually sterile and odorless when it first reaches the skin. The smell comes from bacteria on the surface, which feed on those oily secretions and break them down into volatile acids.
Testosterone reshapes this system during puberty. Androgens promote the development of apoeccrine glands, a hybrid type with a secretory rate roughly seven times higher than standard sweat glands in response to the same nerve signals. Sweat rate in adult men is more than double that in adult women. Importantly, this gap doesn’t exist in prepubescent boys and girls, whose sweat output (adjusted for body size) is comparable to adult women’s. The difference is locked in during puberty through hormone-driven gene expression, not through ongoing testosterone levels in adulthood. Giving women testosterone doesn’t increase their sweat production, and blocking testosterone in men doesn’t reduce theirs. The glands are essentially reprogrammed once, during adolescence.
The Chemicals Behind the Smell
The signature “sweaty” smell in male armpits comes largely from a compound called 3-methyl-2-hexenoic acid, or 3M2H. It’s produced when skin bacteria metabolize the proteins and fatty acids in apocrine sweat. The scent is sharp and acrid, quite different from the milder smell of ordinary perspiration.
Men’s sweat also contains much higher concentrations of a group of steroid compounds called 16-androstenes, including androstenone and androstenol. These are the closest thing humans have to pheromones. Their concentrations are significantly higher in male armpit sweat than in female. Androstenone is often described as unpleasant or urine-like at higher concentrations, while a related compound, androstadienone, appears to improve women’s mood in controlled studies. Women exposed to male armpit extracts or purified androstadienone reported increased positive mood and reduced negative mood, an effect that didn’t occur with androstenol alone or a neutral control. So some of what makes men “stinky” may have once served a social signaling function.
Diet Makes It Worse
What men eat changes how they smell, and red meat is the biggest culprit. In a study where 17 men alternated between a meat-heavy and meat-free diet for two weeks, 30 women rated the body odor collected on armpit pads. The results were consistent: odor from the meat-free period was rated significantly more attractive, more pleasant, and less intense. The likely mechanism is that digesting red meat produces sulfur-containing compounds and other byproducts that get excreted through sweat. Men who eat more red meat on average than women (which population-level data consistently shows) are compounding an already stronger baseline odor.
Clothing Traps the Problem
Fabric choice plays a surprisingly large role. Polyester, the most common synthetic in athletic wear and everyday shirts, is hydrophobic. It repels water but attracts oils and bacteria. Because apocrine sweat is lipid-rich, polyester absorbs more of the bacteria’s primary nutrient source (sebum) and binds more odor-causing bacteria to its fibers than cotton does. Nearly every bacterial species tested in textile research adhered more strongly to polyester than cotton.
Cotton has its own drawbacks. Its higher moisture retention keeps bacteria active for longer after the fabric dries. But in practice, the intense, lasting stink people notice on gym clothes and undershirts is overwhelmingly a polyester problem. If you’ve ever noticed that a synthetic shirt smells rank after one wear while a cotton tee survives two, this is why.
When Body Odor Becomes a Medical Issue
Normal male body odor exists on a spectrum, but there’s a clinical condition called bromhidrosis where the smell becomes excessive or abnormal. It happens through the same basic mechanism (bacterial decomposition of sweat gland secretions) but at a level that persists despite regular hygiene. Apocrine glands in people with bromhidrosis are target organs for androgens and contain high levels of a specific enzyme (a type of 5-alpha reductase) regardless of gender. This means some men (and some women) are genetically predisposed to produce secretions that bacteria find especially easy to convert into foul-smelling acids.
A less common form involves eccrine (watery) sweat. Normally that sweat is nearly 100% water and essentially odorless. But when eccrine sweat softens the protein keratin in skin, bacteria can degrade that too, producing smell in areas like the feet or skin folds where moisture gets trapped.
What Actually Reduces the Smell
Since the odor comes from bacteria breaking down sweat rather than from sweat itself, the most effective strategies target bacteria. Antiperspirants containing aluminum compounds reduce both moisture and bacterial growth. Washing with antibacterial soap in the armpits and groin directly lowers the population of odor-producing microbes. Wearing natural fibers or moisture-wicking blends that don’t trap sebum can slow bacterial buildup between washes.
Dietary changes help too. Reducing red meat intake measurably improves how body odor is perceived by others. Cruciferous vegetables (broccoli, cabbage), garlic, and heavy alcohol consumption can also increase odor intensity through similar metabolic pathways. None of this eliminates the hormonal baseline that makes men smell stronger, but it narrows the gap considerably.