I'm not going to presume to tell you what to do.
As with many things in life, you must examine the facts and make a decision for yourself about what's best in your own situation.
That decision will not be the same for everyone. It will depend on your circumstances and your point of view.
My aim here is simply to present the facts as I know them, with proper sources as my foundation, and to tell you what I do, and why.
The rest is up to you.
Let's start with the basics...
In terms of knowing whether it's a safe, natural substance, it helps to know how diatomaceous earth is formed.
It's made from the fossils of microscopic aquatic algae called diatoms. Over many thousands of years, diatoms collected in rivers and streams. Their skeletons are made from silica, and it's that which is mined from those areas today.
The mined substance is then ground into a fine powder.
The fossilised diatoms are made of almost pure amorphous silicon. This is important, because it's the crystalline form of silica which can cause silicosis - a form of lung cancer(1).
So it's important when buying it to make sure the crystalline component is as low as possible. In the US, a product is considered safe if it is less than 2% crystalline silica, but that's considered high in other countries.
Here's a simple scientific explanation for how diatomaceous earth works for external parasites like red mite and lice:
"Diatomaceous earth causes insects to dry out and die by absorbing the oils and fats from the cuticle of the insect's exoskeleton. Its sharp edges are abrasive, speeding up the process. It remains effective as long as it is kept dry and undisturbed"(2).
Food grade diatomaceous earth is generally available from food and feed stores, or online. Wherever you buy from, for use with your chickens make sure it...
This brand contains less than 1% crystalline silica. (It doesn't say that anywhere on the product, so I wrote to the manufacturer who confirmed). It also has a free powder duster, which we'll see the benefit of later in this article.
There are many claims made for diatomaceous earth related to humans. I'm not covering those in this article - I'm concerned solely with its uses for chickens.
The scientific evidence for controlling internal parasites, that is parasites like worms inside the chicken's body, is much less clear - in fact, I've been able to find no conclusive evidence that it's effective for this.
It's also important to remember that unhatched worm larvae in the gut won't be affected by DE. For that reason I personally don't use it as a wormer.
Studies have shown that free range chickens who had DE added to their food were heavier and laid more and larger eggs containing more yolk and albumen(2).
So feeding diatomaceous earth to chickens in the right amount may be beneficial to their egg production.
Because it's known that diatomaceous earth can help control parasites, it can be added to dust baths for chickens. Dust baths help prevent parasites but they won't deal with an existing infestation quickly enough - for that you'll need to dust it onto the bird.
I'm lucky enough to have a large run, with several different areas the chickens use for their dust baths. They generally prefer to take their dustbath spas in loose earth, and I don't add any DE to those areas - the soil and grit they use is enough to keep parasites away.
I also provide an alternative of a child's sandpit turned into a dustbath in the shade of the fig tree in their run.
Because the earth is contained, I add diatomaceous earth to this dust bath. It's mainly filled with potting compost, which they love, and some ordinary loose soil from the garden. To that, I add diatomaceous earth to make up no more than one quarter of the total.
Mix the DE in well. Having it as only small part of a dust bath means there's not enough of it for the chickens to breathe it in.
Don't leave this out in the rain - we saw earlier that DE is effective only when it's dry. When it gets wet it turns into a sloppy mess.
If you want to experiment with DE in your chickens' feed, the recommendation is to sprinkle it on and then mix it in at the rate of no more than 5% of the total(3). I find it hard to estimate in percentages, so I'd use a quarter cupful to every 5 cups of feed.
If your chicken has a particularly bad infestation of parasites like mites, a dust bath won't be enough. You'll first need to get rid of the mites which are already there.
Parasites tend to gather around the chicken's vent and at the shaft - the bottom of feathers where they meet the skin. Apply the diatomaceous earth there, and wherever else you see mites or lice crawling. Using an applicator like the one that comes with this brand is helpful.
Bear in mind that it's better for both you and your chickens not to breathe it in, so...
As I said at the start, this is a personal decision we should all make for our own situation. Diatomaceous earth can cause sometimes quite heated discussions between chicken keepers, and we must all take the available information and make a balanced judgement.
Personally, I don't use a lot of it, but I do use it in my container dust bath, to dust chickens down if they have obvious signs of parasites, and to dust those parts of the coop where I know mites collect.
So, take the information here and make your decision. Whatever it is, it will be made based on proven studies and the best available information.
A lot of "facts" on the internet are often people's individual views, often based on inaccurate information repeated from poor quality sources.
The information I provide in this article and others is based not just on my own experience, but on evidenced facts from scientific, peer-reviewed research and from highly respected and experienced poultry keepers such as Gail Dammerow.
Some of the sources I have used for this article are these. Direct links are given unless the article is on a "not secure" page.
1. Occupational Safety and Health Administration: Crystalline Silica Exposure - Health Hazard Information. Pub. 2002.
2. Bunch, T. R.; Bond, C.; Buhl, K.; Stone, D.: Diatomaceous Earth. Pub. National Pesticide Information Center, Oregon State University, 2013.
3. Bennet, D., et al: Effect of diatomaceous earth on parasite load, egg production and egg quality of free-range organic laying hens. Pub. Journal of Poultry Science, 2011.
4. Maurer, V. and Perler, E.: Silicas for control of the poultry red mite. Paper published to the Joint Organic Congress, 2006.