A persistent, musty odor can be confusing, but it is a common issue with many possible explanations. Understanding the potential causes, from simple external factors to complex internal processes, is the first step toward finding a solution. This article explores common hygiene and environmental issues first, then progresses toward less frequent, medically significant causes. A sudden or unexplained change in body odor should always prompt a discussion with a healthcare professional to rule out underlying health concerns.
Common External and Hygiene Factors
The most frequent causes of a musty smell are external, relating to clothing care and personal hygiene habits that allow moisture-loving microbes to flourish. A musty scent is often a sign of mildew and mold growth, which thrive on damp fabrics and surfaces. This growth often starts in the laundry process itself.
Leaving wet clothes in the washing machine or a damp hamper for too long creates the perfect environment for mold and bacteria to multiply, and the odor can then be baked into the fibers when dried. Improper drying, such as not allowing clothes to fully air out, also leaves residual moisture that encourages mildew growth. Using too much laundry detergent can be counterproductive because the excess soap residue becomes a food source for odor-causing bacteria in the fabric. Overloading the washer prevents proper circulation of water and detergent, which leaves dirt and bacteria behind.
Personal hygiene practices also contribute significantly, particularly in areas where moisture is easily trapped. Not thoroughly washing or drying skin folds, the groin, armpits, or between the toes allows a build-up of sweat, dead skin cells, and bacteria. The resulting combination of organic material and moisture is an ideal breeding ground for the microorganisms that produce unpleasant odors. Wearing tight-fitting clothing or synthetic fabrics, which trap heat and moisture against the skin, can exacerbate this issue by creating a humid microclimate for bacteria.
Physiological Sources of Odor
Beyond external factors, the body’s natural processes contribute to scent, which can sometimes be perceived as musty. Body odor is primarily generated when bacteria on the skin break down the secretions from two types of sweat glands. Eccrine glands are distributed across most of the body and produce a watery, odorless sweat for temperature regulation.
Apocrine glands, located mainly in the armpits and groin, produce a thicker, protein- and lipid-rich sweat that is initially odorless. It is the metabolism of these fatty compounds by surface bacteria that generates the characteristic, stronger body odor. Certain dietary choices can also influence this process, as volatile compounds from foods like garlic, onions, or excessive alcohol intake are excreted through sweat and breath, temporarily altering a person’s scent profile.
For some, particularly in middle age and beyond, a musty or grassy scent may be related to a compound called 2-nonenal. This molecule is a product of the oxidation of omega-7 fatty acids on the skin, a process that becomes more prevalent with age. This phenomenon is often referred to as “nonenal odor” and can be a naturally occurring, harmless change in scent not necessarily tied to hygiene.
Musty Odor Caused by Infections and Skin Conditions
A musty odor that is localized to a specific area often points toward a microbial overgrowth or skin infection that thrives in warm, moist environments. Fungal infections, such as tinea cruris (jock itch), are a common cause of this localized, damp, or yeasty-musty smell. The fungi break down skin proteins, releasing specific odor-producing compounds, and the smell is often exacerbated by trapped moisture and sweat.
These infections frequently occur in skin folds and areas of friction, with symptoms including a red, itchy, and scaly rash. Bacterial conditions, such as erythrasma and intertrigo, also flourish in these humid, occluded areas of the body, like the groin, armpits, or under abdominal folds. Intertrigo is a rash that results from friction and moisture, and when a secondary bacterial infection occurs, it can produce a foul odor. Erythrasma, caused by the bacteria Corynebacterium minutissimum, is more prevalent in those who sweat heavily, have diabetes, or are overweight, presenting as brown or pink patches. Treating these conditions typically requires specific topical antifungal or antibiotic medications to eliminate the microbial source of the odor.
When the Smell Signals Underlying Health Issues
While rare, a pervasive and distinct change in body odor not explained by hygiene or common causes can signal a serious underlying systemic illness. When organs responsible for filtering waste products are compromised, toxins that would normally be excreted accumulate and are released through the breath and sweat.
Liver disease, especially in advanced stages, can cause a musty or sweet odor, often described as fetor hepaticus, due to the liver’s inability to filter sulfur-containing compounds. Poorly functioning kidneys can lead to a buildup of waste products, which may produce an ammonia-like or urine-like smell that some might interpret as musty. Uncontrolled diabetes can also alter body chemistry, leading to a fruity or acetone-like scent from the overproduction of ketones. If the musty odor is sudden, intense, or accompanied by other concerning symptoms, such as unexplained fatigue, weight changes, or changes in urination, consult a healthcare professional immediately.