When did you last wash your pillow?

Numerous studies have found pillows are likely to be riddled with living and dead dust mites, dust mite faeces, dead skin, and bacteria.

Dr Stephen Archer, a microbiologist at Auckland University of Technology, explains all about the miniature zoo of microscopic life living and feeding off one another inside your pillow.

I love my feather pillow! I’ve had it for 20 years and I even take it on holiday with me. Is it time to ditch it?

There are two main reasons why you should replace your pillow every few years:

• Comfort, when your pillow no longer holds its shape it is time to replace it;
• Hygiene, bacteria will accumulate over time and can start causing allergic reactions.

So should I wash my pillow? Won’t the washing machine ruin the feathers?

You can, and should, clean your pillow. It’s generally recommended you wash your pillow every 2-6 months – how to do so depends on its materials, so check the tag (you should clean your pillowcase far more regularly).

When you’re washing a feather pillow, be gentle. Most can be put through your washing machine and dryer on a gentle cycle but, as with most things, read the instructions as some need dry cleaning.

It’s generally suggested you hand-wash memory foam or latex pillows.

What kinds of germs might end up in your pillow?

Given its close contact with your face, which is covered in microorganisms, your pillow will encounter a lot of human skin-associated microbes, including good and bad bacteria – such as Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae and Enterococcus faecium – as well as good and bad fungi, including a large proportion of household moulds such as Aureobasidium pullulans.

Fungal spores are extremely resilient and spread exceptionally easily, waiting for a moist environment like your pillow to multiply. Studies have shown incredibly high and highly variable numbers of each of these groups (hundreds of thousands to millions). In pure numbers these can exceed what you may find on other “unclean” surfaces, such as your toilet seat or pet food bowls.

Whatever is in your environment can end up on your pillow. So if you have pets, especially those that get on your bed, then you will have more varied microorganisms on your pillow. You may also have some fecal bacteria if you haven’t washed your hands properly or have a flushing toilet with an open door within a few metres of your bed.

What about dust mites?

Another common invader are dust mites. These tiny bugs feed off dead skin cells and microorganisms, like those found in your pillow, and their faeces are the main cause of many household allergens, associated with asthma.

In fact, these faeces can then be used as a food source for the bacteria and fungi in your pillow, leading to a mini ecosystem under your head every night. Washing your pillow will help remove these allergens and dust mites, and tumble drying at hot temperatures will help to kill the microorganisms and dust mites in your bedding.

If you suffer from asthma or allergies, you’ll need a far stricter cleaning and replacement regime.

How can you tell if your pillow is too old?

If you start having skin (allergic reactions or acne) or neck problems, then it’s probably time to replace your pillow.

Other signs include excessive yellowing, smells or your pillow not springing back to its original shape when you fold it in half.

It’s important to note that some people may be more sensitive than others and need to change pillows far more regularly. On the other hand, don’t stubbornly hold on to one out of frugality and not consider it may be causing discomfort that you’ve just gotten used to or can’t see.

The best rule of thumb for me is when I stay overnight elsewhere and can see if I get a better or worst night’s sleep from the pillow there.

What about duvet inners – do we also need to replace them after a certain amount of time?

Since these don’t have the same amount of close pressured skin contact, they should last much longer than your pillow. However, as with everything else, look for signs of wear and keep them on a consistent cleaning regime.

What’s the best way to keep your bedding healthy?

1. Use clean outers that you wash regularly (recommended weekly).

2. Wash the inners and air them out routinely (at least twice a year).

3. Clean yourself before getting into bed if you are dirty.

4. Do not go to bed with wet hair, as this increases bacterial growth.

5. Replace pillows when you start to see or feel that they might be negatively affecting your health.

6. Keep your house clean and dry (moist conditions help microorganisms and dust mites to multiply).

7. Use common sense.

Any recommendations for what the best pillow fillings are in terms of human health?

Firstly, you should consider how you sleep, as this affects how you’ll need to support your spine during sleep. Pick a pillow that you find comfortable in terms of shape and firmness.

As for the accumulation of bacteria, latex and memory foam are less likely to absorb as much sweat or as many bacteria, so the risk of allergic reactions reduces (although this is far from clear in the literature and all pillows will accumulate bacteria).

Overall, your body will be the best judge of what type of pillow you should use – so be aware of it and change as needed.

Where to from here?

In summary, there’s a miniature zoo of microscopic life living and feeding off one another in your pillow (and mattress and duvet) every night, accumulating larger populations and more faeces over time.

Even in an exceptionally clean house, their numbers may exceed the population of Aotearoa and may or may not cause problems with human allergies. You can keep numbers down with regular cleaning but they are there, and they really are on every surface in your house and in the world.

I work in extreme environments and find huge numbers of microorganisms everywhere you wouldn’t expect to find them, including the air (that’s right, there’s always a wide variety of microorganisms –and more than just viruses and spores – in the air).

I often get asked how I deal with knowing all this and no, I do not have a hip-holster of disinfectant on me at all times. In fact, being overly “germ”-averse can lead to bigger problems with underdeveloped immune systems.

Generally, if it’s unlikely to make you sick it isn’t a problem. Manage risks by maintaining good hygiene and use what nature has given you to stop you from getting sick: common sense.

Stephen Archer is a senior research fellow at Auckland University of Technology, researching extremophile microbial ecology from remote sites across the globe. He has published work in numerous leading international scientific journals on microbiology and ecology. He is also a father of five living in West Auckland and, along with his family, is doing his best to live sustainably.