Too much detergent
Counter-intuitively, more soap does not make for cleaner clothes. Rather, it can make them grimier as he soap residue fades colour and attracts more dirt. It can also lead to bacteria build-up in the machine and on clothes, especially in areas where the excess soap holds dirt and doesn’t get washed away, like pleats or collars. Detergent build-up even encourages odor.
Leaving wet clothes in the machine
It can not only lead to stinky clothes and a smelly machine, it can allow mildew to start forming, which can trigger an allergy or asthma attack.
You’d have to leave your clothes sitting wet in the washer for about 24 hours before mildew is likely to start forming. But, for smells’ sake, it’s best to remove clothes from the machine as soon as you can. If you don’t have time to hang them out, try placing them in a plastic basket in a ventilated area or at very least open the washing machine door to let air in.
Overloading your machine
It is tempting to clean your basket full of clothes in one fell swoop to save on time. But, it means the “cleaning” part isn’t really effective and it can also damage the machine. To clean successfully, clothes have to be able to move around inside the drum, so that water and detergent can distribute evenly, lift stains and shake the dirt free. When you overload your machine, you cramp its style in this sense and also strain its suspension and bearings from overwork.