Why does my dishwasher smell bad?

The smell is decomposing food debris, and it accumulates in a small number of predictable places. Working through them in order resolves nearly every case without any product.

The filter is the first and most common. Most modern dishwashers have a removable filter assembly in the base, and many owners have never taken it out because the manual mentions it briefly. It traps food particles by design and needs rinsing under a tap, monthly or more often. A neglected one can hold a surprising amount.

The spray arms are second. Their holes clog with debris and mineral deposits, which both worsens cleaning and leaves residue behind. They usually unclip for rinsing, and a cocktail stick clears stubborn holes.

The door seal and the edge of the door below the seal collect residue that never gets sprayed, since the water does not reach there. Wiping with a damp cloth handles it.

The drain hose is the less obvious cause. If it is not routed with a high loop, or the connection under the sink is partly blocked, waste water can sit in the hose or back up slightly. A smell that is strongest when the door opens after a cycle, rather than when idle, points here.

Once clean, running an empty hot cycle with a dishwasher cleaner or a cup of white vinegar in the top rack clears the remainder.

Two preventive habits help: scrape plates rather than rinsing them, since modern detergents need some soil to work against, and run the machine regularly, because a dishwasher left unused for weeks with residue inside will smell.