A persistent, severe, sewer-like odor emanating from the body can be distressing. This malodor is often linked to volatile compounds the body is either overproducing or unable to process correctly. The smell, which can exit through the breath, sweat, or urine, usually points toward an internal physiological process. Understanding the source involves investigating the complex interactions between gut bacteria, diet, and systemic metabolism. Causes range from imbalances in the digestive tract to underlying metabolic or organ-related health conditions.
Digestive Sources of Volatile Sulfur Compounds
The most common internal source of a sewer or rotten-egg smell is the overproduction of Volatile Sulfur Compounds (VSCs) in the gastrointestinal tract. These compounds, particularly hydrogen sulfide (H2S), are a natural byproduct of gut bacteria breaking down sulfur-containing proteins from food. H2S is known for its distinctive, unpleasant, sulfurous odor.
Diet directly fuels the bacteria that produce VSCs, as high-sulfur foods provide the necessary fuel. Common culprits include cruciferous vegetables, eggs, red meat, garlic, onions, and sulfur-containing preservatives. When consumed, gut bacteria metabolize these compounds, releasing VSCs that are absorbed into the bloodstream.
These gaseous compounds circulate and are expelled through the lungs as bad breath or released through the skin via sweat. An imbalance in the gut microbiota, known as dysbiosis, can cause an overgrowth of sulfur-reducing bacteria, increasing VSC production. This excessive production overwhelms the body’s ability to neutralize the compounds, causing persistent malodor.
Small Intestinal Bacterial Overgrowth (SIBO) exacerbates this issue by allowing excessive bacteria to colonize the small intestine. When bacteria thrive there, they ferment undigested carbohydrates and sulfur-rich compounds earlier in the digestive process. This heightened fermentation results in a large volume of gas, including H2S, which is absorbed and released from the body as an offensive odor.
Systemic Health Conditions Affecting Odor
When major processing organs are compromised, metabolic waste products accumulate and are released through breath and sweat. These systemic conditions involve a failure to properly metabolize or eliminate compounds. Trimethylaminuria (TMAU), or “fish odor syndrome,” is a metabolic disorder that causes a severe, sometimes sewage-like, odor.
TMAU is typically a genetic condition where the body cannot convert the pungent compound trimethylamine (TMA) into an odorless molecule. TMA is produced when gut bacteria break down compounds like choline and carnitine, found in eggs, liver, and certain fish. When the conversion fails, the malodorous TMA builds up and is excreted through all bodily fluids, causing a strong, persistent smell described as fishy or sewage-like.
Liver or kidney dysfunction also leads to systemic odor because these organs filter toxins and waste from the blood. A diseased liver may be unable to break down compounds like mercaptans, giving breath and sweat a musty or rotten-egg smell. Kidney failure causes urea buildup, resulting in breath that smells of ammonia or urine (uremia).
Diabetic ketoacidosis (DKA) is a severe metabolic state where the body burns fat for fuel, producing acidic ketones. One ketone, acetone, is volatile and exhaled, giving the breath a sweet or fruity odor. This illustrates how systemic metabolic failure forces the body to expel chemical waste products.
Odor Caused by Skin and Sweat Interactions
While internal sources are the primary cause of a true sewer smell, external factors involving the skin and sweat contribute to strong body odor. Bromhidrosis is the medical term for excessive odor, occurring when bacteria on the skin break down sweat and skin secretions. Sweat itself is odorless, but its breakdown releases volatile organic compounds that cause the characteristic smell.
Apocrine glands, concentrated in the armpits and groin, secrete a lipid- and protein-rich sweat susceptible to bacterial decomposition. Bacteria, often Corynebacterium species, metabolize these secretions into short-chain fatty acids, which include sulfur compounds that possess a pungent or sulfur-like smell. Poor hygiene allows these bacteria to proliferate, intensifying the odor.
Skin infections can also produce a putrid odor due to bacterial or fungal growth in moist areas like skin folds. Clothing materials that trap moisture and prevent ventilation create an ideal environment for bacteria to flourish, contributing to the external odor.
Seeking Medical Advice and Treatment
A persistent, unusual body odor warrants consultation with a healthcare professional to determine the underlying cause. Medical advice is important if the odor is new, severe, or accompanied by concerning symptoms. These include unexplained weight loss, persistent gastrointestinal distress, vomiting, or chronic fatigue, which can suggest a serious systemic or metabolic disorder.
The diagnostic process begins with a thorough medical history and physical examination, followed by targeted testing. For digestive causes like SIBO, a breath test measures gases produced by bacteria in the small intestine, including hydrogen sulfide gas. If a metabolic cause is suspected, blood or urine tests screen for compounds like trimethylamine to diagnose conditions such as TMAU.
Treatment pathways are specific to the diagnosis, but initial steps involve dietary modification to limit odor-contributing compounds. SIBO treatment may involve antibiotics to reduce bacterial overgrowth, followed by strategies to maintain a balanced gut microbiome. Metabolic disorders like TMAU are managed through a low-choline and low-carnitine diet, while underlying systemic diseases require specific medical management from specialists.