When to wash what: 1  Sheets. 2  At least every two weeks, more often if you sweat a lot. 3  Pajamas. 4  After 3 or 4 wearings (if you shower before bed, you may get a few more). 5  Towels. 6  After 3 or 4 normal uses or more frequently if you play sports.7  Socks and underwear. 8  After each wearing.9  Bras. Sheets. 2  At least every two weeks, more often if you sweat a lot. 3  Pajamas. 4  After 3 or 4 wearings (if you shower before bed, you may get a few more). 5  Towels. 6  After 3 or 4 normal uses or more frequently if you play sports. 7  Socks and underwear. 8  After each wearing. 9  Bras.