Pest Control
Mould mites unmasked: causes, solutions and prevention
Tiny pale specks moving across a damp windowsill or shelf are usually mould mites. They live on mould, so the cure is drying the room out.
Mould mites are tiny, easy to miss and alarming once you notice them moving. They do not bite and they are not a sign of a dirty home. They are a sign of a damp one, and that is where the solution lies.
The short version
- Mould mites feed on mould and fungi, so they only appear where there is damp and mould growth, even if you cannot see it yet.
- They do not bite or spread disease, but they can trigger allergy symptoms in some people.
- Remove the mould, dry the room out and keep it dry. Insecticide does not fix this.
What are mould mites?
The species most often found in homes is Tyrophagus putrescentiae, a mite well under half a millimetre long. On their own they are almost invisible; in numbers they look like a fine, pale dust that moves. You tend to see them on windowsills, shelves, the backs of furniture, wallpaper, books and stored food, wherever mould has started to grow.
They do not bite or burrow into skin. Their bodies, shed skins and droppings can, however, become airborne and cause sneezing, coughing or itchy skin in people who are sensitive to them. Handling mite-infested food can cause an itchy rash sometimes called grocer's itch.
Why do mould mites appear?
Because the conditions suit mould. The usual causes are:
- Condensation and high humidity from drying washing indoors, cooking and showering without extraction, or rooms that are kept cold.
- Leaks from pipes, roofs, gutters or window seals.
- New or newly plastered rooms. Fresh plaster and screed release a great deal of moisture as they dry, and mould mites are often reported in new builds and renovations in the first year or so.
- Still air behind furniture pushed against cold outside walls, inside wardrobes and under sinks.
- Damp stored food such as flour, cereals, dried fruit and pet food kept in a humid cupboard.
Signs of a mould mite infestation
- Mould or mildew, often grey or black spotting on walls, ceilings, sealant or the backs of furniture.
- Fine, moving, pale dust on surfaces near the mould. A magnifying glass or a phone camera on zoom shows them clearly.
- A musty smell in a cupboard or room.
- Allergy-type symptoms that are worse in one room. This is not proof of mites on its own, so look for the other signs too.
How to get rid of mould mites
- Remove the mould. Clean affected surfaces with a mould remover, following the instructions on the product, and wear gloves and a mask. Never mix bleach with other cleaning products. Throw away mouldy soft items you cannot clean.
- Deal with the food. Check dry goods, bin anything affected, wipe the cupboard dry and store food in sealed containers.
- Dry the room out. Ventilate, run a dehumidifier and keep the room evenly heated. Aim to keep indoor humidity below about 60 per cent; a cheap hygrometer tells you where you are.
- Fix the source. Repair leaks and stop water coming in, otherwise the mould and the mites come back.
- Vacuum regularly while the room dries out to remove mites and debris.
Spraying insecticide is not the answer. Mould mites die off quickly once their food and moisture are gone, and chemicals in a damp room add a problem rather than solve one.
How to prevent mould mites
- Use extractor fans when cooking and showering, and open trickle vents.
- Dry washing outside or in a ventilated room with the door closed and a window open.
- Leave a gap between furniture and cold outside walls.
- Keep rooms evenly heated rather than leaving some cold.
- Check regularly for leaks, damp patches and failed sealant.
- Keep dry food in airtight containers.
When to call us, and when to call someone else
Mould mites are a damp problem first and a pest problem second. If the damp has a building cause, such as a leak, failed pointing, bridged damp-proofing or poor ventilation, a builder, plumber or independent damp surveyor is usually the right call. If you rent, report damp and mould to your landlord in writing.
If you are not sure what you are looking at, or you think the specks could be something else, such as stored-product beetles or booklice, send us a photo and we will tell you what it is and who is best placed to help.
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Send us a photo or describe it. We will tell you what it is, whether it needs treating at all, and what it would cost, before anyone comes out.