From what I understand, any soap including sunlight and dawn, is deadly for any insect which breathes through its thorax. Breathing through its undercarriage. So when it skittles through water, it is okay, but sudsy soap actual plugs them up and they die from asphyxiation. Try it on a nest of earwigs!!! RAID and other chemicals, these little buggers just think it is raining outside and amble off. Put a 1/7 or 8 parts water with some dish soap, and voila!!! Instant bug destroyer. They literally may get a foot or two before they are deader than a door nail. Ants are no match either when you pour it down their hole.
I should keep some Dawn handy by the sounds of it. Haven't had chickens long, but we have had to deal with cat fleas before. NOT nice! So we try to keep everything super clean....but they putter outside so it is only a matter of time I think.