Mold

• Mold is perhaps the most frequent culprit of washing machine smells. Mold growth is especially prevalent in machines that are not used frequently because a new cycle is not washing away developing spores. Mold also is likely to occur in machines that sit with the door shut between cycles. This restricts airflow and provides a damp, dark environment that mold thrives in. Stave off mold growth by using your machine regularly or wiping it down with a towel after infrequent use. Dry off the inside drum as well as areas such as the soap dispenser. Keep top-load machine doors open between cycles and crack open the door of front-load machines to allow the washing machine to fully dry and help prevent mold growth.
  
  

Bacteria

• Bacteria can grow in your washing machine because of several factors. It may be left behind by dirty clothes, especially if your machine is older and does not effectively empty. Machines that fail to full empty the washing water in general also can lead to bacteria growth from the sitting dirty water. Service your washing machine if it does not fully empty, and in the meantime, wipe out any excess water after doing a load.
  
  

Detergent Residue

• All washing machines are susceptible to detergent buildup after awhile. The buildup causes scum and grease, both of which can carry foul odors. The smells can be worse from detergents that contain animal fats, which naturally smell bad. Wipe away any grease buildup you can see, and lift out the removable parts of the agitator to inspect for grease.
  
  

Getting Rid of Washing Machine Smells

• Regardless of the cause of the washing machine smells, several simple approaches should banish the odors from your appliance. First, mix a paste with 1/4 a cup of baking soda and 1 cup of water. Wipe down the inside of the washing machine, including the doors, soap dispenser and around the agitator. Run a warm rinse cycle, without clothes, and smell the machine to see if the odors have disappeared. If not, you can use either white vinegar or bleach -- never use them together in the same cycle, as this produces harmful vapors. Pour a cup of white vinegar or bleach into the soap dispenser and run the washing machine on the hottest cycle, without clothes. Send the machine through an extra rinse cycle to eliminate vinegar or bleach odors and clean away any of the remaining liquids, which could harm clothing.