This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: You forget a load in the machine overnight, and by morning it smells worse than before you washed it. Most of us are familiar with that "wet dishcloth" smell.
Worse, once it has settled into your clothes, it can be difficult to get rid of. So what's going on, and how do you fix it? The answers lie in both biology and textile science, which help explain why some fabrics are affected more severely than others.
Damp fabric at room temperature is close to an ideal microbial habitat. It provides warmth, moisture and abundant food in the form of skin cells, sebum (skin oil) and sweat residues that may survive a normal wash cycle. The bacterium most responsible for the "wet rag" smell is called Moraxella osloensis.
A Japanese study in 2012 traced the smell to a compound this bacterium produces. It also found the species tolerates drying and ultraviolet exposure unusually well—more proof that bacteria can survive the wash and start thriving in a wet load that has not been promptly hung out. It is not only clothes that harbor microbes.
A 2025 study found household washing machines themselves host persistent microbial biofilms (colonies that detergent alone struggles to remove), especially around door seals and in the detergent drawers of front-loaders. Each cycle, that biofilm can reinoculate freshly washed laundry, so clothes can emerge from a "clean" wash already carrying the seeds of the smell. If laundry is left wet long enough or dries too slowly in a poorly ventilated room, fungi can join the bacterial party.
Mold and mildew produce their own volatile compounds, notably geosmin, the molecule behind the "earthy" smell of rain-soaked soil. Human noses are extraordinarily sensitive to it, detecting it at concentrations of just a few hundred parts per trillion. Cotton is hydrophilic ("water-loving"): it binds water readily, leaving fewer places for the oily residues of sweat to lodge inside the fabric.
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