If this question makes you giggle thinking what difference it makes let me tell you many people think that wearing an unwashed bra for few days at a stretch during winters is fine. Since unlike summers you don t sweat too much in winters so your bra doesn't need a wash after every wear. In fact a few days back a friend came and spilt a personal secret to me that she can go without washing her bra for few days at a stretch in winters as there is less of sweat and so practically it doesn't get dirty after