Chickens need to take a bath, in dirt.
Dust baths are how chickens prevent mites and lice from taking hold on their skin and and making them sick. If your chickens have access to a little area of dirt that they can dig up and then throw the dirt around they are all set. IF your birds are in a coop where they don't have access to a little dirt pit you will need to create one for them. Here is what I have done (although my hens have access to the outdoor baths - see above) to make one. I take a low galvanized tub and fill it with a mixture of things: diatomaceous earth (wear a mask when using), sand, dirt, and some fireplace ashes.