The short answer
Dust mites are killed at 60 °C, not 40 °C — which is the single fact that should decide how you wash bedding. Sheets and pillowcases weekly at 60 °C; every three to four days if you have allergies, sweat heavily, or sleep with pets. If a fabric will not take 60 °C, 30 minutes in a hot tumble dryer achieves a similar result. Wash bedding on its own and never more than one duvet cover at a time, or it balloons and nothing else in the load rinses. Skip fabric softener entirely.
Bedding is the laundry most people under-wash and wash too cool. It collects roughly a litre of perspiration a week per person, plus skin cells, body oils and everything that feeds dust mites — and dust mites are the point at which washing temperature stops being about cleanliness and starts being about whether the wash accomplishes anything at all.
The temperature that matters
Dust mites are killed at 60 °C. Below that, washing removes some allergen but the mites themselves largely survive, and they are what most house dust allergy actually responds to.
That gives a clear split:
| Item | Temperature | Why |
|---|---|---|
| Sheets and pillowcases (cotton) | 60 °C | Kills dust mites, removes body oils |
| Duvet covers | 60 °C, or 40 °C if the fabric demands | Less skin contact than sheets |
| Pillows | 60 °C if the label allows | Heavy mite population |
| Duvets and quilts | Per label, usually 40–60 °C | Drum size is the real constraint |
| Linen and delicate weaves | 40 °C | Hot washing shortens their life |
| Silk | 30 °C, hand or silk cycle | Protein fibre, heat-sensitive |
If a fabric will not take 60 °C, the alternative for mite control is a hot tumble dry — 30 minutes at high heat achieves a similar result — or freezing small items for 24 hours, then washing cool to remove the allergen.
How often
| Item | Interval |
|---|---|
| Sheets and pillowcases | Weekly — every 3–4 days if you sweat heavily, are ill, or have allergies |
| Duvet cover | Every 1–2 weeks |
| Pillow protectors | Monthly |
| Pillows themselves | Every 3–6 months |
| Duvet | Every 6–12 months |
| Mattress protector | Every 1–2 months |
Sleeping without a top sheet, sleeping with pets, and going to bed without showering all move these intervals shorter.
The mistakes that shorten bedding life
- Overloading. A duvet cover balloons and traps everything else inside it, so nothing tumbles and nothing rinses. Wash bedding on its own, and never more than one duvet cover at a time.
- Too much detergent. Bedding is a large surface area of fabric and holds residue readily, which is what makes sheets feel scratchy. Use less than you think — the reasoning is in How Much Laundry Detergent You Actually Need.
- Fabric softener on sheets. It coats the fibres and reduces breathability, which is exactly wrong for something you sweat into.
- Over-drying. High heat weakens cotton fibres. Take sheets out slightly damp and finish on a line or an airer.
Buttoning and tying
Fasten duvet cover buttons before washing. An open cover swallows sheets and pillowcases, which then do not wash — and the tangle stresses the seams.
Pillows
Most synthetic and down pillows are washable; foam and latex are not. Check the label, and when in doubt do not.
- Wash two at a time so the drum stays balanced.
- Use a small amount of detergent and add an extra rinse — pillows hold detergent stubbornly.
- Spin at moderate speed.
- Dry thoroughly with dryer balls, breaking up clumps by hand every 30 minutes. A pillow that is not completely dry inside grows mildew where you cannot see it.
Down pillows follow the same rules as washing a down jacket — the drying is the part that determines the result.
Storing spare bedding
- Store clean and completely dry, in breathable cotton bags or on an open shelf
- Avoid sealed plastic boxes, which trap residual moisture and produce a musty smell
- Air stored bedding before use if it has been packed away for a season
Common questions
Is 40 °C really not enough for sheets?
It cleans them, but it does not kill dust mites — that needs 60 °C. If your fabric will not take it, a 30-minute high-heat tumble dry achieves a similar result. For anyone with a house dust allergy, this distinction is the whole reason to wash bedding hot.
How often should sheets really be washed?
Weekly for most people, every three to four days if you sweat heavily, sleep with pets, are unwell, or have allergies. Sleeping without a top sheet also shortens the interval, because the duvet cover then takes the skin contact.
Why do my sheets feel scratchy after washing?
Almost always detergent residue rather than the fabric. Bedding is a lot of surface area and holds surplus surfactant readily. Cut the dose, skip fabric softener entirely, and strip the existing build-up with two detergent-free hot washes.
Can I wash a duvet in a normal machine?
Only if it can tumble freely. A single may fit a large domestic drum; a king will not, and washing one in a machine too small produces a sodden mass that never dries properly. Use a laundrette machine for anything bigger than a single.
Should I use fabric softener on bedding?
No. It deposits a waxy layer that reduces breathability and absorbency — the opposite of what you want in something you perspire into all night. If you want softness, use less detergent and dry with wool dryer balls.