UNDERWEAR should be thrown out every year for health reasons to reduce the risk of urinary tract and other infections, the Good Housekeeping Institute warns.
Failure to do allows bugs such as E. coli and dust mites to flourish, causing problems from urinary tract infections to thrush and allergies, The Sun newspaper reports.
And while in use, underwear should be laundered regularly on the hot wash setting.
The Good Housekeeping Institute (GHI) guide says that despite washing systematically after use, most people's clean underwear contains up to 10,000 living bacteria.
An examination by the UK's leading cleaning company, Dr Beckmann, revealed up to one million bacteria in just two tablespoons of used washing machine water.
Up to 90 per cent of dirty tea towels contained E Coli bacteria, found in human faeces, and supposedly "clean" underwear was disturbingly dirty.
The GHI guidelines for use say should be changed daily, nightwear after three sleeps and bedding once a week, and all washed afterwards at high temperatures.
Pillows need to be laundered every three to six months and duvets twice a year.
But a recent study in the UK showed one in four men wore underpants for two days before washing, and women wore the same nightclothes for a fortnight.
"Pyjamas are worn right next to the skin and we shed skin cells, filled with microorganisms, at a vast rate," the GHI said.
"It turns out there are quite a few washing avoiders out there. These dirty habits are helping bacteria thrive.
"We spend a third of our lives in bed so, although sheets don't wear like clothing, you do need to wash them weekly. Night after night, germs, sweat and skin cells accumulate."
GHI recommended cleaning the washing machine to make sure clothing had the best chance of being as clean as it looked.
A survey conducted by US dry cleaner and launderer Mulberry's Garment Care earlier this year revealed that 18 per cent of men and 10.5 per cent of women don't wash their underwear at all.
Eighteen to 24-year-olds were the most hygienic undergarment cleaners, MSN reported.
Seventeen per cent of men and seven per cent of women report that they do not wash their guest bed sheets before or after having a guest over.
women tended to be more reliable about washing their own bedding.
Seven per cent of men reported washing their bedding only once in the last six months, as compared to just three per cent of women.
Forty-three per cent of women said they wash it every week, while only 31.6 per cent of men did.
1. Wiping out the detergent drawer on your washer to stop soap build-up, and cleaning it thoroughly in hot, soapy water every few months.
2. Running a monthly service wash with hot water and no clothes to rid the machine of mould and bacteria.
3. Checking and cleaning drain filters.
4. Wiping the rubber seal with diluted bleach or vinegar to prevent mould or bacteria build-up.
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