Diatomaceous earth (DE) is a naturally occurring, fine powder derived from the fossilized remains of tiny, aquatic organisms called diatoms. These microscopic algae accumulated over millions of years, leaving behind skeletons primarily composed of silica. The unique structure of DE allows it to function as a mechanical insecticide and absorbent. It works by scraping the pest’s protective outer layer, or exoskeleton, and then absorbing moisture, leading to fatal dehydration. This non-chemical mode of action makes DE a popular, low-toxicity option for pest management around homes and gardens.
Understanding the Grades and Handling Safety
The effectiveness and safety of diatomaceous earth depend entirely on its grade and how it is handled. There are two primary types: Food Grade and Filter Grade. Food Grade DE is uncalcined, meaning it has not been heat-treated, and contains a maximum of 2% crystalline silica. This type is generally recognized as safe for use around humans and pets.
Filter Grade, often called Pool Grade, is calcined and contains a much higher concentration of crystalline silica, sometimes as much as 60%. This industrial grade is dangerous if inhaled or ingested and should only be used for filtration purposes, never for pest control. To ensure safety for residential applications, only purchase products explicitly labeled as Food Grade.
When applying any fine powder, including Food Grade DE, wearing a dust mask is important to prevent respiratory irritation. Although Food Grade DE is mostly amorphous silica, inhaling the fine particles can still cause lung irritation. Gloves are also recommended, as the powder is highly absorbent and can dry out skin with prolonged contact.
Applying Diatomaceous Earth for Household Pest Management
For managing pests inside the home, Food Grade DE must be applied as a dry, thin, and unnoticeable layer to be most effective. A puffer or bulb duster is the best tool for this application, allowing the powder to reach into small spaces without creating visible piles. Pests like ants, cockroaches, and bed bugs will actively avoid thick deposits, so a barely visible film is necessary.
Focus the application on areas where pests hide or travel, such as cracks, crevices, and wall voids. Lightly dust under sinks, behind appliances, along baseboards, and inside electrical outlets. For carpeted areas, a fine layer can be sprinkled, left for 24 to 48 hours to allow contact with pests, and then vacuumed up. The powder must remain dry to function, as moisture will render it ineffective until it dries out again.
Incorporating Diatomaceous Earth in Gardens and Pet Care
Garden Use
In the garden, diatomaceous earth provides a physical barrier and direct contact control for a variety of pests, including slugs, earwigs, and squash bugs. A light, even dusting should be applied to the soil immediately around affected plants to deter crawling insects. For pests on leaves, the powder can be lightly dusted directly onto the foliage, focusing on the undersides where many pests hide.
Because DE loses its efficacy when wet, any application outdoors requires reapplication after rain or heavy watering. It is best applied during dry weather and minimal wind to ensure it adheres to the target areas and minimizes drift. Exercise caution when applying it to blooming plants, as it is a broad-spectrum insecticide that can harm beneficial insects, including pollinators.
Pet Care
For pet care, Food Grade DE is often used to manage fleas and ticks in the environment and on the animal. Dusting the pet’s bedding, favorite resting spots, and carpets with a light layer can help control the environmental stages of pests. When applying directly to a dog or cat, rub the dry powder into the pet’s coat, ensuring it reaches the skin, while taking care to avoid the eyes and nose to prevent irritation.
Considerations for Internal Use
Some individuals choose to consume Food Grade diatomaceous earth as a dietary supplement for purported health benefits. Claims often include detoxification, improved digestive health, and enhanced hair, skin, and nail health. For this purpose, a small amount is typically mixed with water or juice and consumed.
The U.S. Food and Drug Administration (FDA) does not regulate diatomaceous earth as a health supplement, and there is limited scientific evidence to support most of these claims. While Food Grade DE is generally recognized as safe when used as an indirect food additive, its effectiveness for internal health purposes is largely anecdotal. Before starting any internal regimen, consult with a physician to discuss potential risks and benefits.