How many times should you wear your clothes before washing them?

The answer is a whole lot more, according to experts, who have warned of the environmental impact of using washing machines and tumble dryers.

With the exception of underpants, a new report by the Society of Chemical Industry (SCI) urges us to do our laundry less frequently.

Not only will this help to reduce the amount of microfibres entering the environment, it will mean less energy and water is used – and fewer greenhouse gases.

The report looked at several academic studies on the impact of washing clothes. One found that a T-shirt typically worn 100 items is washed and dried 50 times.

But 70% of the carbon emissions created during the life of a cotton T-shirt were down to washing and drying, with only 30% coming from production.

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David Bott, head of innovation at the SCI, said: “If we all washed our clothes slightly less frequently, then it can make a big impact.

“You certainly don’t have to wash outfits every day, except possibly ­undergarments. As well as microfibres, the detergents go into the sewage system.”

It is recommended that you should wear tops and dresses four to five times before washing, bras six times, pyjamas for seven nights, wool jumpers 10 to 15 times and jeans between 15 and 30.

According to Professor Mike Berners-Lee, who specialises in assessing the impact of climate change, tumble dryers produce about three times as much CO2 as washing machines.

The SCI report also says that washing less frequently will make clothes last longer.

Each year 350,000 used but wearable clothing items are sent to ­landfill. Instead, techniques such as spot cleaning, steaming, sponge cleaning and brushing, will help make clothes last a lot longer between washes.

For example, hanging knitwear as close as possible to a shower without it getting wet can remove odours. For mud, wait until it has dried and use a clothes brush to remove it. A small sponge, warm water and a drop of apple cider vinegar is advised to remove food stains.

Salt is also good for stubborn wet stains such as red wine, tea and tomatoes. Leave for 20 minutes before scrubbing or soaking.

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