Diatomaceous earth (DE) shows some ability to reduce certain internal parasites in chickens, but the evidence is limited and inconsistent. It is not a reliable standalone dewormer. One peer-reviewed study found that adding 2% DE to chicken feed reduced specific worm species in one breed of hen but had no measurable effect in another, more parasite-resistant breed. If you’re dealing with a serious worm infestation, DE alone is unlikely to solve the problem.
What the Research Actually Shows
The most cited study on this topic, published in Poultry Science, tested DE as a feed additive in free-range organic laying hens. The results were a mixed bag. One breed (Bovan Brown) that received DE in their diet had significantly fewer Capillaria worms based on fecal egg counts, fewer birds infected with cecal worms (Heterakis), and a significantly lower overall cecal worm burden compared to untreated birds. But in the other breed tested (Lohmann Brown), which was naturally more resistant to parasites, DE made no statistically significant difference in worm counts or fecal egg counts.
The researchers concluded that DE “has the potential to be an effective treatment to help control parasites,” particularly for organically raised flocks where conventional dewormers may not be permitted. That phrasing matters: “help control” is very different from “eliminate.” DE reduced parasite loads in some cases but didn’t clear infections entirely.
How DE Is Supposed to Work Against Worms
Diatomaceous earth is made of fossilized diatoms, tiny organisms with silica-based shells. The proposed mechanism is purely physical, not chemical. As the microscopic particles move through the digestive tract, their rough, abrasive surfaces are thought to scrape against worm bodies, damaging their outer layers. The porous structure of diatom shells also absorbs moisture, which can dehydrate parasites. This combination of abrasion and desiccation is what reportedly damages or kills worms and their eggs.
This physical mechanism is well established for external insects, where DE can effectively dry out and destroy the waxy coating on bugs like ants and beetles. Whether the same process works as reliably inside the warm, wet environment of a chicken’s gut is less certain, which is why study results have been inconsistent.
Common Chicken Worms and Their Impact
The most common internal parasite in chickens is the large roundworm (Ascaridia galli). Cecal worms (Heterakis) and hairworms (Capillaria) are also widespread, especially in free-range and backyard flocks where birds have constant contact with contaminated soil. These parasites cause general poor condition, reduced appetite, lower egg production, weight loss, and inactivity. In severe cases, large numbers of roundworms can physically block the intestinal tract, which can be fatal.
It’s worth noting that the study showing DE’s benefits found effects primarily against Capillaria and Heterakis. There is little evidence that DE is effective against the most common parasite, large roundworms, or against tapeworms.
How to Add DE to Chicken Feed
The standard ratio used in research is 2% of the total feed weight. So for every kilogram of feed, you’d mix in about 20 grams of DE. Blend it thoroughly so it’s evenly distributed rather than clumped in one spot. You must use food-grade DE only. This is a critical distinction.
Food-grade DE contains less than 1% crystalline silica and is composed mostly of amorphous silica, which is far less harmful. Pool-grade (also called filter-grade) DE has been heat-treated, which converts the silica into a crystalline form that is genuinely dangerous to both animals and humans. Pool-grade DE should never be used around livestock, in coops, or in feed. Food-grade products must also meet strict limits on heavy metals, containing no more than 10 mg/kg each of arsenic and lead.
Respiratory Risks to Your Flock
Even food-grade DE poses real risks when it becomes airborne. Chickens have an unusually delicate respiratory system. They lack a diaphragm and rely on a network of air sacs that are highly susceptible to irritation. Inhaling fine DE dust can cause sneezing, coughing, inflammation, and with prolonged exposure, chronic respiratory disease. Veterinarians generally advise against applying DE directly onto birds for this reason.
The risk is highest in enclosed or poorly ventilated coops where dust lingers in the air. If you’re dusting nesting boxes or coop floors, do it while your birds are outside and allow the dust to settle before they return. Wear a mask yourself. Repeated inhalation can cause throat irritation, coughing, and in severe long-term cases, a lung condition called silicosis.
DE for External Parasites
Many chicken keepers also use DE to combat mites and lice, but the evidence here is equally underwhelming. A study published in the Journal of Applied Poultry Research found that DE applied as a liquid solution reduced northern fowl mites only when used for two consecutive weeks, and the effect lasted less than two weeks after that. Compared to other treatments tested, DE ranked near the bottom in effectiveness, below sulfur, neem, and kaolin clay. Veterinary sources generally advise against relying on DE for external parasites.
How DE Compares to Standard Dewormers
Conventional dewormers work through chemical mechanisms that target worm biology directly. Fenbendazole, one of the most commonly used poultry dewormers, achieved an 83.7% reduction in fecal egg counts in studies on domestic chickens. Levamisole, another option, showed 71.8% efficacy. These aren’t perfect numbers either, and researchers have noted concerns about growing anthelmintic resistance in some flocks. But they represent a much more predictable and substantial reduction than what DE delivers.
For organic or pasture-raised operations where synthetic dewormers aren’t an option, DE at 2% of feed may offer a modest supplementary benefit as part of a broader parasite management strategy. That strategy should include rotating pastures to break worm life cycles, keeping coops clean and dry, and monitoring fecal egg counts periodically to catch heavy infections before they become dangerous. Relying on DE as your only line of defense against a confirmed worm problem is risky, particularly if your birds are already showing signs of illness.