Your clothes come out of the wash smelling faintly of the machine. Not dirty exactly, just musty, worse on towels, worst after something has been left in the drum overnight. You have been using more detergent, which is making it worse.

That is the mechanism most people get backwards. Modern machines use very little water, and detergent that is not fully rinsed away stays behind as a soft residue on the drum, the outer tub you cannot see, and especially in the folds of the door seal. That residue holds moisture, moisture holds bacteria and mould, and the smell is biological. More detergent is more residue, so the instinct makes the problem worse every wash.

A machine cleaner is formulated to be the opposite of a detergent. It is built to break down that residue and the film growing on it and then rinse completely, run on an empty hot cycle so it circulates through the pump and the hoses as well as the drum.

Which is why an empty cycle matters. Doing it with a load in means the clothes absorb what should be going down the waste.

Here is the limit. It will not reach mould you can already see on the rubber seal. That has to be wiped by hand, and if it has gone black in the folds it is often permanently stained even once it is dead. Pull the seal back and look before you decide this failed.

It is also not a fix for a blocked filter or a pump full of hair and coins, which produce their own smell and need opening up.

And it is maintenance. Monthly on a front loader that gets heavy use. The 52-week framing is honest about that: this is a habit you are buying, not a one-off repair, and leaving the door open between washes does half the job for free.