Do you wash your bed pillows at least twice a year? You should. Not only do they have sweat in them because sometimes we do sweat at night but they are loaded with dust mites. Dust mites live on dead skin and we constantly shed. So yes, you should be washing your pillows at least twice per year. If they have started to yellow from the summer of sweating Interior Design Info shares a method of bringing them back to white again. I have pretty bad allergies so I wash mine a little more often and I add 10 to 15 drops of eucalyptus oil to my wash water because eucalyptus oil kills dust mites better than bleach. I even make a solution of distilled water with both eucalyptus oil and lemon balm oil in it, adjusted to a fine mist and spray it around my bed to keep the dust mites down. It smells so fresh.