Sheets need to be changed and washed on a weekly basis. Washing sheets removes the dirt, dust and sweat that builds up on them over time.
Use warm to hot water when washing bed sheets. The warmer temperature of the water kills bacteria living on the dirty sheets. A hot dryer setting also kills bacteria. To prevent damage to the sheets, check the care label on the sheets to be sure the fabric can tolerate warm or hot settings.
Put away sheets only when they are completely dry, as any dampness can cause mildew. Replace sheets when signs of wear and tear appear.