Research has found that some parts of your fridge can be up to three times dirtier than a toilet seat. The dirtiest area of the fridge is usually the door, which is warmer and provides a perfect breeding ground for bacteria. Incorrect food storage, such as putting milk in the door, can also contribute to the growth of bacteria. It is recommended to deep clean your fridge at least three times a year, using a soapy water solution and ensuring that all surfaces are dried properly.