The cotton fibers are ruptured due to growth of fungus
It is obvious that clothing pick up dirt from the environment and work areas. In fact, a human shed about 500 million skin cells and a liter of sweat every day. Our clothing absorbs this sweat and other secretions from our body. The body heat makes these dirty clothing a nice place for bacteria or fungi to live and grow. The problem starts when these bacteria living on skin get involved. They live by feasting on wearer’s sweat and skin oils and start breaking the proteins into smelly by-products. Also, the natural body fluids like sweat, urine which are not visible and stains from food and drinks which are visible, produce odor in our clothing. Hence after a certain level and time all these things need to be removed from the clothing.
Washing of clothing hence not only kills the bugs but also removes all unwanted impurities thus making the garment look better, more hygienic and smell fresh.
If fabric is not washed for prolong periods, this is what happens. This image is Seen using foldscope at Dayalbah Educational Institute, Agra