Yes, sometimes bacteria can build up under your system and cause an odor. Usually this only happens when a unit is left bonded on for long periods of time. This problem can easily be managed by more frequent washings and using a regular maintenance schedule.

There's a product made specifically to help manage this called Jorgen Bio Enzyme. Bio Enzymes are highly activated, non-pathogenic bacterial cultures that have the ability to digest compounds such as fats, oils, cellulose, detergents, sugars and starches. Directions: Spray on as a dry shampoo or apply and leave in to eliminate odors. This product works great as a scalp cleanser, odor and oil eliminator and a spray on leave-in product.