I thought so, too, until I read this post: https://www.backyardchickens.com/threads/did-i-just-hurt-my-chicken-with-permethrin-10.1641146/Chickens can be dipped, and they love warm water because it relaxes them. I've done it using Permethrin liquid concentrate. Use common sense not to dip them when there are cold temps. Permethrin dust can be used in cold temps. Dont forget to treat inside the coop, nest boxes etc.
Here's a link, scroll down where you can read about Permethrin dips:
https://www.backyardchickens.com/ar...-fleas-dealing-with-external-parasites.74599/
It could have been more of a dosage/ dilution issue, though.