I put mine in something warm like a towel or sweater and cover them up and put my hand on top for awhile and they seem to like that and they warm I never used a heating lamp can't afford but they all lay down with their beer snuggled and so cut and cozy
So I don't know call me crazy, but I need to share something. I knew NOTHING about chickens or even how to take care of a baby chick. So I like many of you google every single day all day long looking for help and answers to every thing I had a question for. Anyways YOUTUBE helped a lot too...
My mom used this for human head lice and it didn't affect us and my dad and some other chicken owners use it in a bucket and their chickens were also fine