A colleague once told me she washed her bed sheets every week and I had a small moment of existential crisis.

How often do I wash my sheets? Definitely not weekly. Is it fortnightly? Monthly? Am I a filth wizard?

I started running through excuses in my head: I don't have a dryer and in winter in Hobart it takes years for things to dry. I have a small washing machine and I need to prioritise clothes washing. I'm being environmentally friendly by using less water.

I decided I needed to know if my lethargic approach to washing the sheets is genius time management or just basic slobbiness, so I hunted down some people who know things about bugs in bedding, organising and cleaning to see what they think.

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Is sheet washing a weekly habit or monthly chore?

Do you really need to change your bed linen more than once a year? ( Unsplash: Jessica Castro )

Susanne Thiebe is a professional organiser in Sydney who helps clients who are feeling overwhelmed to better sort out their homes and time. She says the majority of the people she works with wash their bed linen every week out of habit, not need.

"Australians seem to change their sheets weekly," she says.

"I find my clients don't even question it. They just do it because their mum did it."

Hobart-based professional cleaner Amanda Graham says the few clients of hers who ask for their sheets to be changed get it done fortnightly.

"That seems to be what people want, when they're paying for it," she says.

Ms Graham says she did a quick poll of her friends to gauge their bed-changing habits and says it ranges from weekly for her friends in Cairns, out to six weeks for friends in cooler climates.

"I'm going to say the average is about three and a half weeks," she says.

So it looks like I'm not the only one slacking off in the laundry department. There does seem to be a decent amount of variation when it comes to Australians and washing sheets.

Changing sheets too regularly can have its drawbacks

How often do you wash your bed sheets? It's either not often enough, or too often, depending on who you ask. ( ABC Open: LizD )

Ms Thiebe says washing bed linen out of habit rather than need can lead to people actually forming even grosser habits by accident.

"A lot of people like the washing, but they don't like putting the sheets on and they don't like putting them away," she says.

"There are a lot of people who don't get around to putting new sheets on and they just end up sleeping on their mattresses and put the doona on top."

Ms Thiebe says it's best to plan a day when you not only have time to strip and wash the doona covers and sheets, but also have time to dry them and put new sheets on.

Don't forget to wash the actual bedding, not just the covers

Washing bed sheets is one thing, but getting them dry can be a whole other level of difficult, especially in the colder states over winter. ( ABC Open: Kevin Parsons )

Ms Graham says while most people are pretty good with cleaning the sheets, they'll often forget to clean or change what lies underneath.

"Have you ever noticed if you go to an Airbnb place or something like that … how filthy the mattress protector or underlay is?" she says.

"I would say most places I've stayed, the underlay or mattress protector is filthy. It makes me feel gross."

Ms Graham recommends mattress protectors, underlays, doonas and pillows be washed at least every six months, if you're able to dry them properly afterwards.

Not washing your sheets — what's the worst that can happen?

A 2018 study in the UK by a laundry company found 3.8 per cent of Brits washed their sheets once a year. Yep, just once in 12 months.

You can only imagine the smell that would emanate from annually cleaned bedding, but is it actually bad for you?

Maybe. Never-cleaned bedding might grow mould and even contain fungi spores that could promote things like tinea or ringworm to take a hold on you.

Dust mites could be a problem

Unwashed bedding can also become home to creatures.

Stephen Doggett is a hospital scientist and head of medical entomology in NSW Health Pathology. He knows a lot about the creepy-crawlies that like to bunk up with us in bed.

Tips to keep dust mites down Dust mites can be a real hazard for those with an allergy. Here are head of medical entomology in NSW Health Pathology Stephen Doggett's tips for keeping them out of your boudoir: Vacuum regularly. At least weekly, maybe more depending on your situation

Vacuum regularly. At least weekly, maybe more depending on your situation Wash your bed linen weekly

Wash your bed linen weekly Avoid shagpile carpet or rugs and if your allergies are bad, avoid carpet in the bedroom altogether

Avoid shagpile carpet or rugs and if your allergies are bad, avoid carpet in the bedroom altogether Go for hard furnishings over soft furnishings

Go for hard furnishings over soft furnishings Don't make your bed — let as much air and light get to your sheets as you can

"The potential insects; the main one would be dust mites," Mr Doggett says.

Dust mites are the most common critters found in beds. They eat the bits of us we leave behind — skin cells, sweat, seminal fluids — and if you don't wash your bedding often, there's more food for the dust mites and so more dust mites.

"We're pretty sloppy, humid creatures," Mr Doggett says.

"We sweat a lot and beds get moist and that sets up conditions favourable to the dust mites."

Dust mites are bad news for people who are allergic to them, particularly those with asthma, so washing your bedding weekly and vacuuming regularly will help keep the mites at bay.

Bed bugs are the tiny vampires of the bed

Bed bugs aren't as common as dust mites, but they can be a real pain in the bum and back and sides and anywhere else on you that they bite.

They eat what's inside us. The bugs bite humans to suck our blood, leaving their victims with itching, rashes, or in very rare, extreme cases, anaphylactic shock.

"Bed bugs are not pleasant creatures," Mr Doggett says.

"They bite you in the night, they'll defecate the blood on the mattress and the sheets get all these black spots."

Bed bugs are found all over the globe and are most common in areas with high density of humans, and places where lots of people come and go — hotels, airports, backpackers, for instance.

"The term bug itself … was first used for bed bugs," Mr Doggett says.

"It derives from the Middle Ages in England when people were sleeping and got bitten in the middle of the night, and they thought it was a ghost or spirit. The term bug actually meant ghost or spirit of the dead."

Don't strip your sheets off the bed unless you have time to put new ones on again. ( Unsplash: Volha Flaxeco )

Bed bug infestations can be very hard to get rid of. The bugs often actually live in the walls near a bed, and this means one infected residence in an apartment block can quickly turn into an infested complex as they move between flats through the walls.

"They're very expensive to control and a lot of people just don't have the fiscal resources to pay for control," Mr Doggett says.

Regularly changing your sheets and airing your mattress is a good way to keep an eye out for bed bugs, but cleaning alone might not get rid of them.

If you find yourself with bed bugs, you may need to call a pest controller in to help get rid of them.

If you have a furry friend that sleeps in the bed with you, you might also have to keep an eye out for fleas in your bed.

Fleas can't live in a bed itself for long. They live on hairy animals — usually a dog or cat.

They aren't a big problem in Australia these days, with flea treatments being quite effective at keeping the jumpers away.

So… how often should I actually wash my sheets?

Washing sheets and airing bedding helps keep creepy-crawlies away. ( Pixabay: Stux )

Frustratingly, it seems there's no one correct answer to how often you should wash your sheets.

It all depends on your personal health conditions, what you get up to in that bed (wink wink), where you live, the season, and if Fido's got fleas and so on and so on.

The main tips I'm taking away from all this icky boudoir talk is to think about what really needs washing to avoid mindlessly washing for no reason and ending up with piles of laundry on my couch and never making the bed again.

It's not laziness. It's for cleanliness.