When did you last change your pillows? I don’t mean the pillowcase, I mean actually binning your lumpy old excuse for a head rest and starting afresh?

Hard to remember, isn’t it? Well, I can guarantee you’ll be getting new washable ones pretty soon after you’ve read the rest of this, because it turns out pillows are filthy. We’re not just talking your own bodily fluids (up to a litre of sweat a night) and dead skin cells (half a pound a year, apparently), but all that of former lovers too.

It gets worse… research by Dr Arthur Tucker, a principle clinical scientist at Barts and The London NHS Trust, found that 45% of people in the UK have never washed their pillows and duvets, even though up to a third of the weight of a two-year-old pillow is made up of dead skin and dust mite faeces.

[Related story: The best laundry guide to washing your duvets and pillows … ever!]

There can be up to 10 million dust mites in one bed alone – and their faeces and body parts can cause hay fever, eczema and asthma, while the bacteria in our beds can cause colds, flu and diarrhoea.

Pillow problem

According to a new study by bedding company sleepypeople.com, although almost everyone (92%) knew about the unseen horrors that can breed in the warm and cosy environment of the bed, people would only consider picking up a new pillow if their existing pillow had become lumpy (64%), looked stained (46%) or failed to pass the ‘sniff test’ (41%).

Meanwhile, Slumberdown has revealed that the majority of us (66%) throw our pillows and duvets away and buy new ones, rather than washing them, which wastes more than £200 million of bedding each year. More than 14 million units of the 21 million sold every year end up in landfill.

[Related story: 9 tips for picking and buying the perfect pillow]

Ex appeal

The sleepypeople.com study also found that almost 18% of both men and women are sleeping on a pillow that at least one other ex has slept on.

Paul Coulter, from sleepypeople.com, says: “Clean pillowcases and sheets aren’t enough to remove an ex from your bed as so much of their skin and sweat will have seeped into your pillows. It’s hardly conducive to a good night’s sleep - for you or your new partner.”

So if you’re planning on switching bedfellows anytime soon, you should really switch your pillows too.

How to tell when it’s time for a new pillow

Yvonne Manomano, cleaning operations manager at Handy says: “Pillows should be washed at least twice a year. In addition to the usual dust and dead skin cells, they also tend to accumulate the oils from face lotions and make-up removers.

“But remember that even if you regularly wash your pillows, there will come a time at which they no longer serve the purpose and should be tossed.

“The best way to check whether you should throw away your pillow is to fold it in half and see if it springs back into shape. If it doesn’t, it is time for a change.”

Home hygiene expert Dr Lisa Ackerley adds: “Just because it looks and smells clean, it doesn’t mean it’s hygienically clean. People have this notion that simply putting dirty items into a washing machine will kill all germs, but that's just not the case.

“Contagious bacteria and viruses such as influenza and E.coli can survive low temperature washing, increasing the potential risk of infection for your family.

“For laundry washed at low temperatures, a disinfectant proven to kill 99.9% of bacteria in temperatures as low as 15°C (such as Dettol Antibacterial Laundry Cleanser) will get it hygienically clean.”

What’s your pillow type?

Annabel Sheen, editor at worldstores.co.uk says: “Synthetic pillows need to be changed much more frequently than feather or down pillows. A lower quality synthetic pillow will have a lifespan of only six months.

“Whatever its quality, a synthetic pillow will gradually flatten and clump over time. However, a synthetic pillow offers the greatest support for a variety of sleeping types – side sleepers, deep sleepers, light sleepers.

“A feather or down pillow has a much longer life, but requires regular plumping and shaking. The down pillow is the most luxurious, but not as good for support: best for those who sleep on their back – and aren’t affected by allergies!”

What about pillow cases?

Sheen says: “The pillowcase material – silk, cotton, polyester – is largely a matter of preference. A key tip for pillowcase care is frequent washing – think how many hours of contact the case receives! Change your pillowcases more regularly than your pillow, choose a thick material if possible, and one that will let your pillow breathe – keep your pillow relationship healthy.”

When did you last wash or change your pillows? Let us know in the Comments section.