A shower removes the smell you have right now, but not whatever keeps producing it, which is why a stubborn odor can be back within hours. The useful question is where it keeps coming from: your skin’s bacteria, your clothes, the area around the anus, or something inside the body. Most of these sources are ordinary and fixable, though a smell that lingers despite good hygiene is sometimes a sign of a treatable condition worth showing a doctor.
How Fresh Sweat Turns Back Into Odor
Sweat from the glands in your armpits and groin has no smell when it first leaves the skin.1TrAC – Trends in Analytical Chemistry. Endogenous and microbial volatile organic compounds in cutaneous health and disease The smell comes afterward, when bacteria that live on everyone’s skin break it down into strong-smelling acids and sulfur compounds.2TrAC – Trends in Analytical Chemistry. Endogenous and microbial volatile organic compounds in cutaneous health and disease One of these acids is pungent even in tiny amounts.3PubMed Central. Microbiota and Malodor—Etiology and Management A different skin bacterium converts a building block in sweat into isovaleric acid, a main cause of cheesy foot odor.4TrAC – Trends in Analytical Chemistry. Endogenous and microbial volatile organic compounds in cutaneous health and disease A shower lowers the bacteria for a while, but they rebound and go back to work with the next round of sweat.
The groin and the crease between the buttocks tend to smell worse than other spots. They hold the same kind of odor-producing sweat glands as the armpits, and these warm, closed folds trap moisture where bacteria multiply quickly. A smell there can easily mix with traces of stool and read as “poop.” Sitting for long periods presses the area closed and adds heat.
Healthy skin is slightly acidic, and the mix of bacteria living on it depends on that acidity. Harsh alkaline bar soaps can upset the balance, while mild, skin-pH cleansers are gentler on the skin’s bacteria.5PubMed. The concept of the acid mantle of the skin: its relevance for the choice of skin cleansers Body hair in the groin and buttock crease gives sweat and bacteria more surface to cling to, so some people notice less odor when they keep it trimmed short.
What does help is washing the buttock crease and groin directly instead of letting water run over them, then drying the folds thoroughly, since damp skin restarts bacterial growth fastest. Use a mild or skin-pH cleanser on sensitive areas. For some people, an antiperspirant on the inner thighs or buttocks cuts the sweat.
Timing can show whether sweat is the main driver. Sweat odor is usually worst after exertion, a hot day, or a long stretch in the same clothes, and it builds gradually through the day. A smell that appears within minutes of washing is one clue that leakage or drainage may be involved.
When Your Clothes Are Holding the Smell
Polyester, nylon, and similar synthetic fibers cling to the oily, fatty compounds in sweat.6PubMed Central. Biological and Chemical Processes that Lead to Textile Malodour Development Washing leaves some of these odors behind, and they build up over many wash-and-wear cycles.7Textile Research Journal. Retention and release of odorants in cotton and polyester fabrics following multiple soil/wash procedures That’s why clothes can smell fresh out of the dryer yet turn smelly once body heat warms them, a problem often called “permastink.”8PubMed Central. Biological and Chemical Processes that Lead to Textile Malodour Development Cotton releases these odors in the wash much more easily than polyester does.9Springer. Microbial survival and odor in laundry
Detergent works by lifting dirt into the wash water, but oily residue on synthetic fibers can stay put, so a garment looks and feels clean while still holding odor. Fabric softener and too much detergent can leave a coating that traps oils and bacteria, so using less can help some garments. The smell often shows up first where fabric touches skin most, such as the crotch seam and waistband of underwear.
Bacteria can also live in the fabric itself. Bacteria from the armpit can form a sticky film on fabric, and some synthetic fabrics favor particular bacteria that are rare on skin.10PubMed Central. Biological and Chemical Processes that Lead to Textile Malodour Development Cotton left damp and drying slowly can produce a compound with a strong fecal smell.11Springer. Microbial survival and odor in laundry So underwear or towels dried slowly in a damp spot can literally pick up a poop-like odor. Cotton underwear absorbs moisture, which helps, but it has to dry fully before the next wear.
To test whether clothes are the culprit, warm a freshly washed pair of underwear in your hands and smell it. Try wearing only cotton underwear for a few days and see whether the smell changes. Check your towels too, since a sour towel recoats clean skin.
For stubborn odor, dry clothes quickly and fully rather than leaving them damp in the machine. Don’t overfill the washer, so water and detergent reach every item. Replace old synthetic underwear and gym clothes that stay smelly after washing.
Leakage and Drainage Around the Anus
A persistent bad odor near the anus often comes from simple causes such as irritated skin or hemorrhoids.12Hemocure. Persistent Bad Odor Despite Personal Hygiene: Is It a Sign of a Fistula or Skin Leakage? Swollen hemorrhoids can also keep the anus from closing fully, so small amounts of mucus or stool seep out without any sense of an accident. Small folds of skin left behind by hemorrhoids can trap stool, and dry toilet paper alone struggles to clean there.
Wiping harder makes it worse, because repeated rubbing irritates the skin and creates a moist, sore area that smells stronger. Gentle cleaning after a bowel movement, with a rinse or a fragrance-free wet wipe, then patting dry, removes what dry paper leaves behind.
An anal fistula is a small tunnel that forms between the inside of the anus and the skin nearby.13Guts UK. Perianal Disease Most people with one notice drainage around the anus that can smell foul and contain blood or pus.14Nebraska Medicine. What is an anal fistula and how is it treated? It can also cause pain, irritation, and a lump near the anus.15Guts UK. Perianal Disease Because the tunnel keeps draining, washing the skin does not stop the smell.
A fistula often shows up as stains of yellow, brown, or bloody fluid on underwear between bowel movements, and the smell returns within hours even right after a shower. A fistula rarely heals on its own and usually needs treatment by a surgeon. Plain sweat odor does not leave stains of pus or blood on underwear, so any such stain is a reason to see a doctor rather than keep scrubbing.
A similar draining tunnel near the base of the tailbone, called a pilonidal sinus, can also release strong-smelling pus, especially with pressure or long sitting.16Hemocure. Persistent Bad Odor Despite Personal Hygiene: Is It a Sign of a Fistula or Skin Leakage? It sits in the cleft above the buttocks, while a fistula opens next to the anus, so the location of the sore spot gives a hint about which it is. Both can flare up: a lump forms and becomes tender, then drains, and the pain often eases afterward. That on-and-off pattern is a reason to be examined.
Leakage, as opposed to sweat, tends to look different. The odor is centered on the buttocks, not the armpits. Brown marks appear on underwear despite careful wiping, and it’s worse after bowel movements or loose stool. A doctor can check for weak muscles or hemorrhoids causing minor seepage.
Skin conditions in folds can smell too. Hidradenitis suppurativa (HS) is a long-term skin condition that causes painful lumps and abscesses in the armpits, groin, and buttocks. Bacteria breaking down sweat and pus in these abscesses create its unpleasant odor.17Canadian Hidradenitis Suppurativa Foundation. Managing HS Odor | Understanding The Cause Of The Odour
Vaginal Odor That Can Be Mistaken for Other Smells
Bacterial vaginosis and trichomoniasis are the most common causes of genital odor in women, and both are relatively easy to diagnose and treat.18Ovid / Journal of Lower Genital Tract Disease. Genital Malodor in Women: A Modern Reappraisal Still, in about a third of women with genital odor, no cause is identified.19Ovid / Journal of Lower Genital Tract Disease. Genital Malodor in Women: A Modern Reappraisal
Because the vagina, anus, and groin folds sit close together, a smell from one area can be hard to place, and clothing carries it everywhere. Bacterial vaginosis usually smells fishy, often stronger after sex, and unusual discharge often accompanies an infection. Smell with itching, burning, or a change in discharge points toward a vaginal cause, while a smell with none of these needs a wider search.
Bacterial vaginosis comes from a shift in the vagina’s normal bacteria and is not a sign of poor hygiene, so more washing will not fix it. Douching can upset the balance further and worsen odor. Trichomoniasis is a sexually transmitted infection, and a partner may need treatment at the same time or it can return. A simple swab test at a clinic can confirm an infection.
Smells That Come From Inside the Body
Substances made by gut bacteria can pass from the intestine into the blood. How fast food moves through the gut and how leaky the gut wall is both affect how much gets through.20PubMed Central. Microbiota and Malodor—Etiology and Management These compounds can then leave the body in sweat, urine, and breath, where a shower can’t touch them. Constipation can slow the gut and give bacteria more time to make smelly compounds, so changes in bowel habits are worth noting.
Some drugs and their breakdown products travel through the body and leave in urine, feces, sweat, and breath, causing unpleasant odor.21Science. Nasty Odor as a Drug Side Effect A new smell that started with a new medicine is worth raising with your doctor or pharmacist.
In trimethylaminuria, or fish odor syndrome, the liver cannot break down a fishy-smelling compound, so people with it give off a fishy smell through sweat and breath.22PubMed Central. Genetic analysis of impaired trimethylamine metabolism using whole exome sequencing It is usually caused by changes in a gene the liver needs for this step, so it is often lifelong.23PubMed Central. Genetic analysis of impaired trimethylamine metabolism using whole exome sequencing A person with a metabolic cause may notice the smell all their life, or it may flare with stress, exercise, or certain foods, which is useful to tell a doctor.
Garlic, onions, and strong spices release compounds through sweat. Red meat and sulfur-rich foods like cabbage may add to odor for some people, and alcohol is partly released through skin and breath. Keeping a food and smell diary for two weeks can reveal a pattern.
Odor from within behaves differently from surface odor. Your breath may carry the same smell, it often appears all over rather than in one fold, and it can seem to follow you into clothes and onto sheets. A blood or urine test can check for metabolic causes. It is a less common explanation than skin, clothes, or leakage, so it makes sense to rule those out first.
When You Smell It but Others Don’t
Olfactory reference syndrome is a strong, persistent belief that you give off an offensive body odor when others can’t smell one.24Cambridge Core. Delusions of Body Malodour: The Olfactory Reference Syndrome It often comes with repeated checking, washing, or covering up the supposed smell, and a sense that others are reacting to it.25Cambridge Core. Delusions of Body Malodour: The Olfactory Reference Syndrome Most people with it say they actually smell the odor themselves.26PubMed Central. Olfactory Reference Syndrome: Demographic and Clinical Features of Imagined Body Odor It’s unclear whether they are extra-sensitive to normal body smells or are smelling something that isn’t there.27PubMed Central. Olfactory Reference Syndrome: Demographic and Clinical Features of Imagined Body Odor
A smell can seem real for several reasons. Some people may be unusually aware of faint scents on their own body that others never notice. Real phantom smells can also arise from the nose or sinuses, such as chronic sinus infection or mouth and throat problems, so a medical check is reasonable. Anxiety can heighten attention to the body, which leads to more checking, and the checking makes the worry stronger.
To find out whether others can smell it, ask a trusted, honest person to tell you directly. Noticing the smell even right after a fresh shower in clean cotton can be one clue among several.
People with it often feel intense shame and may not tell anyone, so it can go unrecognized for years. Hearing “I can’t smell anything” may bring only brief relief, because the belief returns, which is part of why professional help matters. Talking therapy and certain medicines used for anxiety and obsessive thinking can help, so raising it with a doctor is a step toward relief, not an admission of something imagined.
When to See a Doctor and What to Expect
Get checked if you notice any of these:
- Drainage, blood, or pus near the anus or tailbone
- Painful lumps or boils in the armpits, groin, or buttocks
- Unusual vaginal discharge or a fishy smell
- A smell that started after a new medicine
- A smell that lasts weeks despite cotton clothing and careful washing
The doctor will ask where the smell is strongest and when it started. A gentle look and feel around the anus can reveal hemorrhoids or a fistula opening. A swab can check for vaginal infections, and a urine test can check for fish odor syndrome if it’s suspected.
To prepare, note when the smell is worst and what makes it better. Bring a list of your medicines and supplements. Mention any underwear staining or drainage, even if it’s embarrassing, and say whether others have noticed the smell.
If nothing on the warning list applies, try two weeks at home first. Switch to cotton underwear and dry laundry quickly. Wash folds directly with a mild cleanser and dry well, and use moist wipes or a rinse after bowel movements. See whether the smell changes before deciding on a visit.