You stink because bacteria on your skin are feeding on your sweat and producing foul-smelling waste products. The sweat itself is nearly odorless when it leaves your body. It’s the microscopic organisms living on your skin, especially in warm, moist areas like your armpits, groin, and feet, that break down proteins and fats in sweat and release pungent compounds in the process. That’s the short answer, but several factors determine how much you smell and why it might be getting worse.
How Bacteria Turn Sweat Into Smell
Your body has two main types of sweat glands. The ones covering most of your skin produce a thin, watery sweat that’s mostly salt and water. These don’t cause much odor. The real culprits are a second type found in hairy areas like your armpits, groin, and scalp. These glands activate during puberty and secrete an oily fluid packed with proteins, fats, and steroids. Bacteria on your skin treat this fluid like a buffet.
Two groups of bacteria dominate your armpits: Corynebacterium and Staphylococcus species. Together, they account for roughly 77% of the microbial community living there. Different species produce different smells. Corynebacterium breaks down sweat components into fatty acids that smell goat-like or cumin-like. Staphylococcus hominis produces a sulfur-containing compound that smells like rotten onions or meat. Even in trace amounts, these sulfur compounds are among the most pungent chemicals your body produces. If your feet are the problem, a different species (Staphylococcus epidermidis) is likely breaking down an amino acid in your foot sweat into isovaleric acid, which has a distinctly cheesy smell.
Hormones Play a Bigger Role Than You Think
Hormonal shifts directly change how much you sweat and what your sweat contains, which changes how you smell. This is why body odor often appears for the first time during puberty: those oil-rich sweat glands in your armpits only switch on when sex hormones rise. But puberty isn’t the only hormonal turning point.
Reproductive hormones like estrogen and progesterone influence skin blood flow and sweating rate. Higher estrogen promotes heat dissipation, increasing blood flow to the skin and the likelihood of sweating, which can push more odor-producing compounds to the surface. Progesterone does the opposite, promoting heat conservation. This is why many women notice their body odor shifts at different points in their menstrual cycle, during pregnancy, or around menopause. Menopause in particular can trigger increased sweating and changes in scent as hormone levels fluctuate and eventually decline.
Foods That Come Out Through Your Skin
Garlic and onions are the most common dietary offenders. When you eat garlic, your stomach breaks down its sulfur compounds into byproducts like allyl methyl sulfide. This molecule doesn’t get fully metabolized. Instead, it circulates through your bloodstream and gets excreted through your sweat, urine, and breath. That’s why “garlic breath” can persist for hours after eating: the smell isn’t just coming from your mouth, it’s coming from inside your body.
Other sulfur-rich foods like cruciferous vegetables (broccoli, cabbage, cauliflower), red meat, and certain spices like cumin and fenugreek can similarly contribute to stronger body odor. Alcohol is another trigger, since your body metabolizes it into compounds that are partly excreted through sweat. These dietary effects are temporary, typically lasting anywhere from a few hours to a day or two depending on how much you ate.
Medications That Increase Sweating
If you’ve recently started a new medication and noticed you smell worse, the drug may be increasing how much you sweat. Several common medication classes are known to cause excess sweating as a side effect. Antidepressants are frequent offenders, particularly SSRIs (like fluoxetine and paroxetine), SNRIs (like venlafaxine), and older tricyclic antidepressants. These drugs affect the brain’s temperature regulation center, ramping up sweat production.
Opioid pain medications, including codeine, tramadol, and oxycodone, trigger sweating through a different pathway involving histamine release. Thyroid medications and corticosteroids can also shift your sweating patterns by altering hormonal feedback loops. If you suspect a medication is making you smell worse, that’s worth bringing up with whoever prescribed it, since switching to a related drug sometimes resolves the issue.
Medical Conditions That Change How You Smell
Sometimes persistent body odor signals something happening inside your body that goes beyond normal bacterial activity.
Bromhidrosis is the clinical term for abnormally foul-smelling sweat. It ranges in severity from odor only noticeable after exercise (mild) to a strong smell present even at rest (severe). It can be a primary condition caused by overactive nerves stimulating your sweat glands, or secondary to another health issue like hyperthyroidism, other endocrine disorders, or hormonal changes during menopause.
Diabetes can produce a distinctive fruity or nail-polish-like smell on the breath. This happens when blood sugar is poorly controlled and the body starts burning fat for energy instead of glucose, producing chemicals called ketones. Acetone, one of these ketones, is exhaled during breathing and has that characteristic sweet, chemical scent. This is a sign of diabetic ketoacidosis and needs prompt medical attention.
Liver disease can cause breath and body odor resembling rotten cabbage, due to sulfur compounds building up when the liver can’t process them properly. Kidney dysfunction can produce an ammonia-like or urine-like smell as nitrogen-containing waste products accumulate in the body instead of being filtered out.
Trimethylaminuria is a rare genetic condition where the body can’t break down a compound called trimethylamine from food. It builds up and is released in sweat, urine, and breath, producing a strong fishy odor. People with this condition often struggle for years before getting a diagnosis because the condition is so uncommon that many doctors don’t think to test for it.
What Actually Helps Reduce Body Odor
Since bacteria are the primary cause, the most effective strategies target either the bacteria themselves or the moisture they need to thrive.
Antiperspirants containing aluminum salts work by physically blocking sweat glands, reducing the amount of moisture that reaches your skin surface. Less moisture means less bacterial activity and less odor. Standard deodorants only mask the smell or contain antimicrobial ingredients to reduce bacteria, but they don’t stop sweating. If regular antiperspirants aren’t enough, clinical-strength versions with higher concentrations of aluminum salts are available over the counter.
Washing with low-pH soaps or applying topical acids to your armpits can also help. Your skin’s natural acidity helps keep odor-causing bacteria in check, and many conventional soaps are alkaline, which temporarily raises skin pH and creates a more hospitable environment for those bacteria. Acidic products restore that balance. Some people find success applying glycolic acid or similar products to their underarms after showering.
Beyond topical fixes, wearing breathable fabrics (cotton, linen, moisture-wicking synthetics) helps sweat evaporate rather than pooling on your skin. Synthetic fabrics that don’t wick moisture tend to trap sweat against your body, giving bacteria more time and material to work with. Shaving or trimming armpit hair can also reduce odor, since hair increases the surface area where sweat and bacteria accumulate.
If you’ve tried all the standard approaches and still notice a persistent, unusual smell, that’s worth investigating with a doctor, particularly if the odor is new, has changed in character, or is accompanied by other symptoms like unusual thirst, fatigue, or changes in urine color. Sometimes the nose knows something is off before a blood test does.