DE is microscopically very sharp and can definitely cause internal cuts to the lungs and prolonged exposure could be bad. Dust masks are usually required when using it. If he hasn't been exposed since, I think he just needs time to heal.
But if you want to try to get rid of the mites, maybe @chickens really would have a suggestion... she lives in Canada. I don't know anything about the regulations there or how readily available permethrin is. It's usually sold as Poultry Dust and there's no egg withdrawal time for hens so I would think it should be safe... and legal...?
But if you want to try to get rid of the mites, maybe @chickens really would have a suggestion... she lives in Canada. I don't know anything about the regulations there or how readily available permethrin is. It's usually sold as Poultry Dust and there's no egg withdrawal time for hens so I would think it should be safe... and legal...?