How often should you wash your bras? By the book, you should wash them every day. Body oils and sweat can accelerate the deterioration of your bras, and daily washing removes these elements before they can cause too much damage.
Practically speaking, many women wear a bra multiple times before washing. If you're rotating through your bras and wearing a different bra every day, you may be able to go a week or two between washes. If you're in a hot weather climate, though, sweat may require you to wash your bras immediately after taking them off, instead of getting multiple wears between washes.
To wash your bra: use a gentle detergent - preferably a bleach-free, fragrance-free detergent - and hand wash your bras in the sink.
If you just aren't a fan of hand washing, you can wash some types of bras in a lingerie bag in the gentle cycle of your washer. You should fasten the bra hooks so they don't catch on other laundry or on the bag while in the washer.
To dry your bra: let your bras air dry, preferably laid flat. NEVER put your bras in the dryer as this can dramatically shorten the lifespan of your bras, and it can severely damage them.
NOTE: Some types of bras should NEVER be washed in your washer, even in a lingerie bag on gentle cycle! Molded cup bras and pre-formed bras, like seamless bras and some padded bras - should never be washed in a washer.
Washing a pre-formed or molded cup bra in a machine can cause the cups to wrinkle or deform, and the wrinkles will show under form-fitted clothes and t-shirts. Washing these bras in a machine is the fastest way to ruin them!
Taking Care of Your Bras
Washing Your Bras
Storing Your Bras
Caring For Underwire Bras
Caring For Molded Cups