You open the door on a load that has just been washed and what comes out is damp and faintly sour. Not dirty, exactly. But not clean either. Some machines go musty, like a towel left in a gym bag. Some go properly eggy. Either way the clothes now smell of the machine.
Worth saying early: this is almost never a broken appliance. It is an appliance that has been fed.
There is a film in there, and things live in it
Inside every washing machine a thin greasy layer builds up - on the drum, behind the rubber door seal, in the detergent drawer, along the drain hose. It is detergent that never rinsed away, fabric softener, body oils and skin cells off your clothes, lint, and in hard-water areas limescale for all of it to grip onto. The name for that layer is biofilm.
Bacteria and mould colonise it because it is warm, permanently damp and full of food. The sour wet-towel smell is their waste. The rotten-egg version is sulphur-reducing bacteria, and those tend to sit in standing water in the filter trap or the drain hose rather than the drum itself.
The four things feeding it
Too much detergent. The largest cause, and the one people find hardest to accept. Surfactants only rinse away cleanly when there is enough water to carry them out. Pour in double what a load needs and the surplus does not work twice as hard - it stays behind as a tacky film on the drum and on the fabric. Caps and pods make this easy, because a cap gets filled by eye and a pod is one fixed size whether you are washing six shirts or a packed drum. If you have never sized a dose on purpose, start with how much laundry detergent to use.
Fabric softener. Softener works by leaving a waxy layer on fabric. That is not a side effect, it is the mechanism. And it does not distinguish between your towels and the inside of the dispenser, which is why softener compartments turn to grey sludge faster than anything else.
Washing cold, every time. Awkward, this one, because cold washing is better for your clothes and your bill and it is what we would tell you to do - do laundry sheets work in cold water goes through the real limits. But 30C is not warm enough to kill anything. Cold is right for the laundry. It is not sufficient for the machine.
Shutting the door. A sealed drum, with a puddle in the seal and warm damp air above it, is close to ideal growing conditions. So is a finished load left in overnight.
Clearing it out, in the order that works
Jumping straight to the hot cycle without cleaning the seal first is why most attempts disappoint.
1. The door seal. Peel back the rubber lip at the front of the drum. Behind it is a channel that traps water, hair, tissue and eventually black spotting. Wipe it out with a cloth and hot water. This is where most of the smell lives.
2. The drawer. Most pull all the way out after a press on a release tab. Scrub the compartments and the roof of the cavity, then put it back dry.
3. The filter. Behind a small hatch at the bottom front. Lay a towel down first, because water will come out. Clear the lint, rinse the mesh, screw it back in firmly.
4. Then the maintenance wash. Empty drum, the hottest cycle the machine offers - 90C if it has one, 60C at minimum. Heat does the work. Run it monthly and the film never establishes. If the machine is also furred with scale, how to remove limescale from a washing machine is a separate acid job.
Stopping it coming back
Door and drawer ajar between washes. Load out when it finishes, not in the morning. One hot empty cycle a month. And dose deliberately rather than generously - which is where format matters more than brand.
A detergent sheet is dosed by being one sheet. It goes into the empty drum before the clothes, never into the drawer, so the drawer stops being somewhere that grows anything. It tears along a perforation, so a half load takes half a sheet. There are no dyes, brighteners or bleaches in ours - three fewer things capable of leaving a deposit. If the loading part is new to you, how laundry detergent sheets work covers it, and where to put laundry detergent settles the drawer question for every format.
What switching will not fix
Changing detergent does not remove a biofilm that already exists. If your machine smells today it will still smell next week on a new one. Clean it out by the four steps above, then change what goes in so it does not rebuild.
Two other things worth being straight about. Our sheets are non-bio, so no enzymes - and enzymes break down exactly the body oils that feed a biofilm, which is what heat and the monthly empty cycle are covering for. Our sheets also carry 1% fragrance, and there is no fragrance-free version at the moment. If a completely scent-free wash is what you are chasing, that is a fair reason to look elsewhere.
Questions people actually ask
why does my washing machine smell like rotten eggs
A rotten-egg smell is sulphur-reducing bacteria growing in standing water, and they usually sit in the filter trap or the drain hose rather than in the drum itself, which is why cleaning the drum alone rarely fixes it and clearing the filter behind the bottom hatch does.
how do i get the smell out of my washing machine
Clean the door seal, the drawer and the filter by hand first, then run an empty maintenance wash on the hottest cycle the machine offers - 90C if it has one, 60C at minimum - because heat kills what is growing and the hand cleaning removes what it is growing on.
does vinegar clean a washing machine
Partly - white vinegar is mildly acidic, so it will loosen limescale and cut light soap film, but it is not a disinfectant at laundry dilution and will not shift an established biofilm, which makes it a reasonable addition to a hot empty cycle rather than the fix on its own.
should i leave my washing machine door open
Yes - leave the door and the detergent drawer ajar between washes so the drum can dry out, because a sealed drum holds warm damp air and a puddle in the door seal, which is close to ideal growing conditions for the bacteria and mould that cause the smell.
can laundry detergent cause a washing machine to smell
Yes - detergent that does not rinse away is one of the main things a biofilm feeds on, and the usual cause is overdosing rather than the detergent itself, because surplus surfactant has no water left to carry it out and settles as a tacky film on the drum.
how often should i clean my washing machine
Once a month is enough for most households - one empty hot cycle on the highest temperature plus a wipe of the door seal - with the filter and the drawer done every couple of months, and monthly treated as a minimum rather than a target if you only ever wash cold.
Where that leaves you
Clean it properly once, then stop feeding it. If you want to change the detergent part, our 60-pack of eco-friendly laundry detergent sheets is one sheet per load, torn to size, into the empty drum. It comes with a 30-day money-back guarantee, and a subscription can be cancelled any time by email or live chat - no fees, no notice period. Clean the machine first, though. That bit is still on you.