Most bras should be washed every week, but this varies depending on the type of bra and how often it is worn. If you wear a full-cup bra most days, then you should wash it each day. If you only wear a half- or quarter-cup bra occasionally, then you can probably go without washing it for several weeks without any adverse effects. When in doubt, always err on the side of caution and wash your bras regularly to protect them from bacteria and other contaminants that may cause odors or irritations.