Diatomaceous earth (DE) is a fine, chalky powder made from the fossilized remains of tiny aquatic organisms called diatoms. It works primarily as a physical insecticide, killing bugs by damaging their outer coating and drying them out. But people also use it in gardens, in animal feed, and as a health supplement, with varying degrees of evidence behind each use.
How It Kills Insects
Unlike chemical pesticides, diatomaceous earth doesn’t poison insects. It kills them mechanically. The powder is made up of microscopic particles with sharp, irregular edges. When an insect crawls through DE, the particles attach to its outer shell (the cuticle) and work in two ways: they absorb the waxy lipid layer that keeps moisture inside the bug’s body, and they create tiny abrasions in the shell itself. Both actions cause the insect to lose water rapidly, and it dies from dehydration.
The shape of the diatom particles matters. Rounder particles tend to absorb moisture faster, while sharper, more angular particles do more physical scraping. Either way, the result is the same: the insect dries out and dies within hours to days, depending on the species and how much powder it contacts.
Common Pest Control Uses
DE is most popular for controlling crawling insects like fleas, bed bugs, ants, cockroaches, and garden pests. For indoor flea control, you can sprinkle food-grade DE onto carpets, rugs, and furniture, and along the outer borders of your home. It begins killing fleas within a few hours, but leaving it in place for at least 48 hours before vacuuming gives it time to work on eggs and larvae too.
For garden use, DE is applied around the base of plants or directly on foliage to target slugs, aphids, and other soft-bodied pests. One important limitation: DE only works when it’s dry. If it gets wet from rain or watering, it stops being effective until it dries out again. Once the moisture evaporates, it leaves behind a thin film that resumes its abrasive action. You’ll need to reapply after heavy rain or any time the powder is visibly washed away.
A thin, even layer works better than a thick pile. Insects will actually avoid walking through large mounds of powder. The goal is a light dusting they can’t easily detect or navigate around.
Effects on Soil and Plants
Gardeners sometimes add diatomaceous earth (technically called diatomite in its raw mineral form) to soil, hoping to improve drainage and water retention. The results are real but nuanced. In sandy soils, adding diatomite increases the volume of smaller pores, which helps the soil hold onto water longer. In one study, field capacity (the amount of water soil retains after draining) roughly doubled when diatomite was added at a 4% rate compared to untreated soil.
However, diatomite alone slightly reduced the amount of water actually available to plant roots. The best results came when it was combined with other amendments like biochar or bentonite clay, which together increased plant-available water beyond what any single amendment achieved. So while DE can improve soil structure, it works best as part of a broader soil management approach rather than a standalone fix.
Use in Livestock and Poultry
Some farmers mix food-grade DE into animal feed as a natural dewormer. The evidence here is mixed and depends heavily on the animal and the type of parasite. In a study of free-range laying hens fed diets with 2% DE, results varied by breed. One breed (Bovan Brown) that was more susceptible to parasites saw significantly lower counts of certain intestinal worms and parasitic eggs. The more parasite-resistant breed showed no meaningful difference from the control group.
This pattern, where DE helps in some situations but not others, is consistent across veterinary research. It may reduce parasite loads in animals already vulnerable to infection, but it’s not a reliable standalone replacement for conventional dewormers.
Health Supplement Claims
Food-grade DE is marketed as a supplement for people too, with claims that it lowers cholesterol, improves bone health, or delivers beneficial silica to the body. The evidence doesn’t support these claims. DE is roughly 85% silicon dioxide, which sounds like it should be a good source of silicon. But a randomized controlled trial found that silicon from diatomaceous earth is poorly absorbed by the human body. Serum silicon levels after eating DE-supplemented food were no different from levels after eating the same food without DE.
The study’s conclusion was blunt: silicon from diatomaceous earth is essentially unabsorbed and has no effect on normal metabolism in adults. The researchers recommended against using it as a bioactive ingredient in functional foods. Any health benefits people report from taking DE supplements are unlikely to come from the silica content itself.
Safety and Inhalation Risks
The biggest safety concern with DE is breathing it in. The fine powder can irritate your lungs, nose, and throat. NIOSH (the U.S. workplace safety research agency) sets a recommended exposure limit of 6 milligrams per cubic meter for amorphous diatomaceous earth, the type sold as food-grade. That’s the level considered safe for workers exposed over a full shift.
For home use, the practical takeaway is simple: wear a dust mask when applying DE, especially indoors or in enclosed spaces. Avoid creating clouds of powder. Once it settles onto surfaces, it poses minimal inhalation risk. Skin and eye protection aren’t specifically recommended by safety agencies for amorphous DE, though the powder can be drying to skin with prolonged contact.
One critical distinction: food-grade DE and filter-grade (calcined) DE are not the same product. Filter-grade DE, used in pool filtration systems, contains high levels of crystalline silica, which is a serious lung hazard linked to silicosis. Only food-grade DE should be used for pest control, gardening, or any application involving people or animals.