Is diatomaceous earth safe, and does it really work?

Diatomaceous earth gets sold as the natural fix for everything. It is not harmless, and it does not kill everything. It is a fine powder made from the fossilised remains of tiny water organisms called diatoms. Insects that crawl through it get their waxy outer layer damaged and slowly dry out. That is a real effect, with real limits, and it is a dust you should not breathe.

If you tried it and still have the bugs, you did not do it wrong. It is a common story with booklice, bed bugs and cockroaches alike, and usually it is because the dust was asked to do a job it cannot do alone.

Is it safe?

• It is a dust. Fine dust irritates the nose, throat and lungs, and it gets into eyes. That matters most for anyone with asthma or other breathing problems, babies and young children who live near the floor, and pets that lie or groom where it was spread.
• Natural does not mean safe to breathe. Flour is natural too, and nobody wants a lungful.
• The type matters. The kind sold for swimming pool filters is processed differently and is not for pest use. Only use a product labelled for insects, and follow that label, including what it says about masks and where not to apply it.
• Do not puff it into the air in rooms where people sleep or children play. Thin and targeted, into cracks and gaps, the way the label says.

Kids, pets, pregnancy and asthma: if anyone at home is in one of these groups, ask a doctor, midwife, pharmacist or vet before you use it, and keep it out of the rooms they use. If someone breathes in a lot of it or gets it in their eyes and feels unwell, get medical help.

Does it work?

Sometimes, partly. Results are mixed for four reasons.

• It has to touch the insect. Insects walk around heaps and thick white lines. A barely visible film inside a crack does more.
• It has to stay dry. Damp makes it clump, and clumped dust does little. That is why it struggles against booklice and silverfish, which live where it is damp.
• It is slow. The insects keep breeding while it works.
• It stays where you put it. Bait gets carried back to where insects hide. Dust only reaches the ones that cross it.

What to use as the main plan

• Booklice and silverfish: the fix is drier air. Ventilate, fix leaks, run a dehumidifier steadily, and dry out cupboards and stored boxes. New homes can stay damp for a while as they dry out, so give it time. See tiny white bugs and the silverfish guide.
• Bed bugs: mattress encasements, hot washing and drying of bedding and clothes, interceptors under the bed legs to track numbers, and usually a professional treatment with follow-up visits. If a service relies on dust alone and you still have them after repeat visits, ask what else the plan includes. The bed bug guide and bed bugs after treatment go further.
• German cockroaches: gel bait in small dots, an insect growth regulator, and monitor traps to count. Dust does not replace bait. After a single sighting, I saw one cockroach shows how to find out if there are more.
• Ants: bait the workers carry back to the nest. See the ants guide.

Follow the label on every product, and keep bait and traps where children and pets cannot reach.

If you still want to use it

1. Buy a product labelled for insects and read the label first.
2. Wear what the label tells you to, and keep children and pets out of the room while you work.
3. Apply a thin film into cracks, gaps and voids, not across open floors, beds or soft furnishings.
4. Keep it dry, and use it alongside the main plan, never instead of it.
5. Clean it up with a damp cloth, not a broom, which throws it back into the air.

Our safety page explains why the label always wins over anything you read online, including here.