Bromidrosis is the medical term for abnormally foul-smelling sweat. The word comes from the Greek “bromos” (stench) and “hidros” (sweat), and it’s diagnosed when persistent body odor is severe enough to affect a person’s self-esteem, social interactions, or quality of life. There’s no precise threshold for how bad the smell needs to be. If the odor is noticeably beyond what’s typical and it’s causing distress, that’s generally enough for a diagnosis.
Two Types Based on Sweat Gland Involved
Your body has two kinds of sweat glands, and bromidrosis is classified by which type is responsible.
Apocrine bromidrosis is the more common form. Apocrine glands are concentrated in the armpits, groin, and around the nipples. They produce a thicker, milky fluid that’s actually odorless on its own. The smell develops when bacteria on the skin break down the proteins and fatty acids in that sweat. Because the armpits are the densest site for these glands, they’re the most common location for apocrine bromidrosis.
Eccrine bromidrosis involves the sweat glands that cover most of your body and are primarily responsible for cooling you down. Eccrine sweat is mostly water and salt, so it doesn’t usually smell. But when the feet are constantly moist and enclosed in shoes, bacteria thrive and produce odor. That’s why eccrine bromidrosis most often affects the feet. It can also result from certain foods, medications, or metabolic conditions that change the chemical composition of sweat itself.
What Actually Causes the Smell
Fresh sweat is nearly odorless. The characteristic stench of bromidrosis is produced by bacteria living on the skin, which feed on sweat components and release volatile compounds as byproducts. Several bacterial species contribute, and each produces different odor profiles.
Staphylococcus hominis is a major player in underarm odor. It breaks down sulfur-containing compounds in apocrine sweat, releasing volatile sulfur molecules responsible for an onion-like smell. Corynebacterium species release a fatty acid called 3M2H, which produces a goat-like odor. Propionibacterium metabolizes glycerol and lactic acid into acetic and propionic acid, creating a vinegar-like smell. The overall body odor a person experiences is a blend of these and other bacterial byproducts, which is why body odor can vary so much from person to person.
Apocrine glands secrete odor precursors as inactive molecules. Bacterial enzymes on the skin’s surface then cleave these molecules apart, releasing the smelly compounds into the air. This is why the odor tends to build over hours rather than appearing immediately after sweating.
Triggers and Secondary Causes
Several factors beyond normal bacterial activity can cause or worsen bromidrosis. Hyperhidrosis, a condition that causes excessive sweating, creates a wetter environment where odor-causing bacteria multiply faster. People who sweat heavily are more susceptible to noticeable body odor simply because there’s more material for bacteria to work with.
Diet plays a direct role. Sulfur-rich foods like garlic, onions, cabbage, broccoli, cauliflower, and red meat can change the chemical makeup of your sweat. Spicy foods, curry, caffeine, and alcohol can increase sweating and alter its odor. These effects are temporary but noticeable.
Certain medications, including penicillin and bromides, can produce eccrine bromidrosis by introducing odor-causing metabolites into sweat. More rarely, inherited metabolic disorders cause persistent changes in body odor. Trimethylaminuria, sometimes called fish odor syndrome, causes the body to emit a strong fishy smell. Phenylketonuria, isovaleric acidemia, and other amino acid metabolism disorders each produce distinctive odors. Medical conditions like diabetes (which can cause a fruity smell from ketone buildup), liver disease, and kidney disease can also change how sweat smells due to toxin accumulation.
How Bromidrosis Is Diagnosed
There’s no lab test for bromidrosis. Diagnosis is clinical, meaning a doctor evaluates it based on the patient’s report of persistent, excessive body odor and a physical examination. The key distinction is between odor that responds to normal hygiene and odor that persists despite regular bathing. A doctor will also try to determine whether the apocrine or eccrine glands are involved, since the location of the odor (armpits versus feet, for example) and the circumstances that trigger it help guide treatment. If a metabolic disorder is suspected, blood or urine tests may be ordered to check for conditions like trimethylaminuria.
Managing the Odor Day to Day
For most people with bromidrosis, the first line of management is reducing the bacterial population on the skin and limiting moisture. Washing with antiseptic soaps targets the bacteria responsible for breaking down sweat into smelly compounds. This alone resolves many mild cases.
Antiperspirants containing aluminum salts are distinct from deodorants. Deodorants mask odor, while antiperspirants actually reduce sweat production by temporarily blocking sweat ducts. For bromidrosis, particularly when hyperhidrosis is a contributing factor, antiperspirants address the root issue more effectively. Wearing breathable, moisture-wicking fabrics and changing clothes after heavy sweating also helps keep bacterial growth in check.
When antiseptic soaps and antiperspirants aren’t enough, topical antibiotics like clindamycin or erythromycin can be applied to reduce the specific bacteria that generate odor. Benzoyl peroxide is another option. These are typically reserved for cases that don’t respond to basic hygiene measures, since prolonged antibiotic use carries a risk of bacterial resistance.
Procedural Treatment Options
For persistent apocrine bromidrosis that doesn’t respond to topical treatments, several procedures target the sweat glands directly. Botulinum toxin injections temporarily block the nerve signals that trigger sweating, reducing both moisture and odor for several months per treatment. Microwave thermolysis (marketed as miraDry) uses microwave energy to permanently destroy sweat glands in the underarm area. Laser treatments offer a similar approach, using heat to damage gland tissue beneath the skin. These procedures are most commonly used for the armpits, where apocrine glands are concentrated, and they reduce both sweating and the substrate that bacteria feed on.