Clothing has varying degrees of being “dirty”. First, every day skin cells die and are rubbed away by the friction of clothing against the skin. If you placed a dark colored piece of clothing under a microscope, you could see small flakes of dead skin. Second, every day people sweat, which gets onto clothing. Third, some kinds of activities are dirtier than others, but even sitting on a bench in a public park can make clothing dirtier. Fourth, some body areas are considered “dirtier” than other parts, mostly because of sweating and the bodily functions that originate in those areas, meaning, a person’s “privates”. Most people would not think of wearing the same pair of underwear day after day because the fabric comes into contact with the genitals and anus.
Children have a unique class of “dirtiness”. In addition to the four points listed above, children typically sit and play on the ground, play with soil, wipe their hands on their clothing, and spill more food on their clothing. So their clothes can become dirty within a short hour or two.