You're late for work, you forgot to put that load of washing on, and your underwear drawer is looking perilously empty.
You know there's a worn bra lurking at the bottom of your laundry basket, but surely, surely you can't pick it out and put it back on. Or can you?
In an interview this weekend, designer Stella McCartney divided fashion and hygiene experts alike when she revealed she doesn't change her bra every day, and claimed that overzealous washing can actually damage our clothes.
The 47-year-old, known for her commitment to the environment, said: "I am incredibly hygienic myself, but I'm not a fan of dry cleaning or any cleaning, really."
So, asks the Daily Mail, is wearing your bra two days running the height of slovenliness?
Or a time-saving short-cut for the sartorially aware? And how often should you be washing the rest of your wardrobe?
Wash: Every wear
Unsurprisingly, all experts agree your knickers should be washed every day, given the garment's proximity to the groin area, and bacteria Staphylococcus aureus that thrives there. If it gets into the skin through a bite or cut this can cause what's called a Staph Infection.
"The bacteria lives in us harmlessly but can cause boils," says microbiologist Dr Katie Laird of De Montfort University, who adds that even among the most scrupulously hygienic bodily matter can still transfer onto undergarments.
"My research has shown that some micro-organisms survive a 40c wash, so if you work in a hospital, nursery or veterinary environment in which you come across ill people, children or animals, I'd recommend washing your clothes at 60c — but 40c is probably sufficient."
Wash: Every one to three wears
Despite Stella's sartorial intervention, Dr Laird still recommends changing bras every day, given there are sweat glands galore in the nearby armpit and the fact Staphylococcus aureus is also present in the armpit. "I would wash clothes in intimate contact with the skin every day," she says, although she stresses this is more of an issue of personal hygiene than disease prevention.
Chartered environmental health practitioner Dr Lisa Ackerley, aka thehygienedoctor.co.uk, meanwhile, is inclined to side with Stella.
"She's probably right to say you don't need to wash your bra every day," she says, but adds that there is "no rule of thumb. It depends on the weather, whether you sweat a lot and how much you (and your friends) can tolerate". A 40c machine wash should suffice.
Wash: Never (But some say every two wears)
Not at all is the verdict from Levi's CEO and President Chip Bergh, who remarked in 2014 that he had never washed his decade-old favourite pair. "If you talk to real denim aficionados, they will all agree you should never put your jeans in the wash," he said.
According to John Reid, managing director of clothing retailer Garment Quarter, washing denim jeans alters the make-up of the material. "Denim jeans should never be thrown in the wash with your other laundry, due to the dyeing process used," he says.
Instead, he recommends washing in cold water with a few capfuls of white vinegar to deodorise and break down stains. Other experts recommend putting your jeans in the freezer overnight to kill bacteria, but Julia Dee, director of Total Wardrobe Care, a company dedicated to keeping clothes in optimum condition, is unconvinced.
"It could make the fibre brittle. I think jeans should be washed every two wears. It makes them softer and more appealing," she says.
If you're a successful clothes designer, that is. According to Stella McCartney: "The rule on a bespoke suit is you do not clean it at all. You let the dirt dry and you brush it off."
Those with more conventional jobs, however, might find the build-up of grime that comes from taking public transport and sitting in stuffy offices unpalatable.
Tailored suit company Hockerty has recommended cleaning after every two to three wears.
This invariably means a trip to the dry cleaner — stick a suit in the washing machine and the shoulder pads, fusing [gluing] and tapes holding the jacket together will change.
Of course, how often men should clean their suits, and how often they actually do, varies wildly.
"I don't think most men dry clean their suits more than twice a year, because it wears them out," says Julia Dee, who thinks men should own three pairs of trousers to every suit jacket, rather than the conventional two, and clean them every eight wears.
"I hate to say this but men have their suits eaten by moths around the crotch because moths are attracted to 'organic stains'."
Meanwhile, she says, due to their proximity to the neck (especially if worn with a tie) and grease from the hair, shirts should be washed at 40c after every wear.
Wash: Every day
It is actually wearing shoes, as much as not changing your socks, that makes your feet smell.
Sweat gets trapped inside shoes, meaning there is more time for the bacteria on the skin to break down proteins in the sweat as it decomposes, especially for those with hormonal changes such as teenagers and pregnant women.
Nonetheless, we should still be changing our socks or tights every day. Pong aside, the sweat absorbed will make it easier for fungal infections such as athlete's foot to spread.
This can give rise to bacterial infections such as Erythrasma that thrives between the toes and leads to brown, scaly skin patches.
"Medical advice to prevent infections includes keeping feet clean, not sharing footwear and changing your socks regularly to avoid moisture build-up," says Lizzie Tipping, owner of sock company Popasox, who suggests washing socks at 60c to kill more germs.
Wash: Every wear
Ever wondered why it's so difficult to stop your exercise clothes smelling? According to Mary Johnson, scientific communications manager for Procter & Gamble, 70 per cent of dirt on our clothes is caused by body soiling invisible to the eye — sweat, skin cells, salt and a waxy fat called sebum, which often get trapped in workout gear.
"This problem is exacerbated in performance clothes that contain channels or grooves that enhance wicking," she adds.
"Body soiling can become trapped in these grooves, making them even more difficult to remove. That is why odours are a common problem with performance fabrics." Letting your workout gear dry out before washing is said to make it easier to clean, while soaking it in white wine vinegar can break down sweat stains.
If the items are made of Lycra, use a cold water machine wash as heat can damage the elasticity.
Wash: At least twice a week
Few of us put on a fresh pair every evening, but perhaps we should, especially if prone to hot flushes or night sweats that could cause smells or staining.
"Technically, you're wearing them for hours, although they're not in such direct contact with your skin," says Dr Laird, whose research has found bacteria can remain on a garment for 21 days if it's not cleaned.
Dr Ackerley adds that it is pyjama bottoms that need changing more regularly, but how often depends on whether you bathe before bed.
"If you're clean before you put your pyjamas on and don't go to the loo during the night, your pyjamas could last you two to three days," she says.