The label is the law. Read your product's label before you mix or apply; the rates here come from the labels listed under Sources.
- Active ingredient
- Diatomaceous earth (amorphous silicon dioxide) (CAS 61790-53-2)
- Chemical class
- Mostly amorphous silicon dioxide, sometimes with very low levels of crystalline silicon dioxide.[1]
- Mode of action
- IRAC Group UNM: Non-specific mechanical and physical disruptors[3]
- Signal word
- Harris Diatomaceous Earth Crawling Insect Killer: Caution[2]
How it works
Diatomaceous earth does not have to be eaten: it absorbs the oils and fats from the insect's outer layer so the insect dries out and dies, and its sharp edges speed that up.[1]
The label says insects that contact or eat the powder die within 48 hours.[2]
Where to put it
Behind and under refrigerators, cabinets and stoves, around garbage cans, sewer pipes, drains and window frames, and in attics and basements; dust insects directly when you can.[2]
For bed bugs, the label says to take the bed apart and dust its joints and crevices, the folds and edges of the mattress, and the cracks and window openings in the bedroom.[2]
Test a small area for staining before treating a surface.[2]
Where it is used
Indoors the label covers cockroaches, ants other than fire, harvester, carpenter and pharaoh ants, earwigs, millipedes, centipedes, crickets, silverfish, fleas, carpet beetles and bed bugs.[2]
Outdoors it can be dusted on patios, sills and window and door frames, around foundations, along ant trails and around sewer pipes and drains.[2]
It stays effective only while it is kept dry and undisturbed.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| Harris Diatomaceous Earth Crawling Insect Killer[2] | P.F. Harris Manufacturing Company, LLC | 3-18 | 85.0% | dust | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| Harris Diatomaceous Earth Crawling Insect Killer | Cracks, crevices and other spots where insects hide, indoors and out | Cockroaches, ants (not fire, harvester, carpenter or pharaoh ants), earwigs, millipedes, centipedes, crickets, silverfish | 1–5 oz per 100 sq ft[2] A light, even, thin layer applied with a bulb or hand duster; in living areas avoid leaving dust on exposed surfaces or putting it in the air. No more than once a week. |
How to apply it, step by step
1. Protective gear
- Avoid getting the dust in your eyes, use adequate ventilation and don't breathe the dust; for prolonged use, the label calls for a NIOSH/MSHA-approved dust mask.[2]
2. Before you spray
- Keep it dry: it works mechanically and stays effective as long as it isn't wet, and the label notes it works less well on crops when relative humidity is above 65%.[2]
- It doesn't control fire, harvester, carpenter or Pharaoh ants.[2]
3. Mixing
- Indoors, use it dry from a hand duster or the bag's applicator; there's nothing to mix.[2]
- Outdoors it can also go on as a slurry of up to 26.5 oz of dust per gallon of water (a 20% mix): fill the tank two-thirds with water, blend in the dust, add the rest of the water and keep it agitated. Slurries are for outdoor use only, never inside living areas.[2]
4. Applying
- Indoors, lay a thin, light coat where pests hide: cracks and crevices, behind and under refrigerators, cabinets, stoves and garbage cans, around pipes, drains and window frames, and in attics and basements; dust insects directly when you can.[2]
- For fleas, treat floors and bedding in and around pet sleeping areas, plus nearby baseboards, carpeting and cracks.[2]
- For bed bugs, take the bed apart and dust the joints and crevices, the mattress folds and edges, and the bedroom's cracks and window openings.[2]
- Outdoors, dust patios, sills, window and door frames, foundations, ant trails and around drains, and reapply no more than once a week.[2]
5. After you spray
- Insects that touch or eat the dust die within about 48 hours; leave it in place while it stays dry, and reapply no more than once a week.[2]
First aid
- In the eyes, hold them open and rinse slowly and gently with water for 15 to 20 minutes, removing contact lenses after the first 5 minutes, and call poison control at 1-800-222-1222 for advice.[2]
Storage, spills and disposal
Safety and environmental hazards
People
The label signal word is CAUTION: it causes moderate eye irritation, and the label says to avoid breathing the dust and to wear a NIOSH-approved dust mask during prolonged use. Breathing it can irritate the nose, and very large amounts can cause coughing and shortness of breath; amorphous diatomaceous earth has not been linked to cancer in people.[2][1]
Pets
Diatomaceous earth is not a poison, and very little is absorbed if it is swallowed; the label allows treating the floor and bedding around pets' sleeping areas for fleas.[1][2]
Bees and pollinators
NPIC reports no wildlife toxicity evaluations but says agencies consider diatomaceous earth unlikely to harm birds, fish or other wildlife.[1]
Fish and water
Diatomaceous earth is practically non-toxic to fish and aquatic invertebrates.[1]
Common questions
- How much diatomaceous earth should I use?
- The Harris label says the amount should usually be 1 to 5 ounces per 100 square feet, applied lightly and evenly.[2]
- Is diatomaceous earth safe to breathe?
- No dust is good to breathe. It can irritate the nose and, in large amounts, cause coughing and shortness of breath, which is why the label says to avoid breathing it and to wear a dust mask for prolonged use.[1][2]
- Does diatomaceous earth work when it gets wet?
- It stays effective only while it is dry and undisturbed.[1]
Sources
- National Pesticide Information Center, “Diatomaceous Earth General Fact Sheet.” npic.orst.edu/factsheets/degen.html (accessed 2026-10-06)
- U.S. EPA Pesticide Product Label System, “Harris Diatomaceous Earth label, EPA Reg. No. 3-18 (EPA-stamped, Apr. 28, 2021).” www3.epa.gov/pesticides/chem_search/ppls/000003-00018-20210428.pdf (accessed 2026-10-06)
- Insecticide Resistance Action Committee, “IRAC Mode of Action Classification Scheme, Version 11.5 (Feb. 2026).” irac-online.org/documents/moa-classification/ (accessed 2026-10-06)