Hi jackietb
I wasn’t familiar with diatominous earth, so looked it up on the internet and reached the same conclusion as Bushsnuffler. From what I read, I would be concerned about the hogs breathing it in as they would likely be in the boxes quite a long time, especially during hibernation. Also I wouldn’t like the thought of them ingesting some of it by mistake. But that’s just my thoughts. It might be worth asking the BHPS, to see what they think.
But boiling water is pretty good at killing the eggs of fleas and ticks, so probably a safer bet and fairly easy with a small box, like a hog box. Maybe not so easy with chicken houses.