Thank you for opting healthcaremagic.com to post your queries and to give us this opportunity to clarify your doubts.
Well, a very strong possibility is that your child gets exposed to something in her daycare to which she is allergic. Most probably, this exposure must be happening while she is leaving the daycare, since none of the teachers have noticed it. The rash
also appears only after coming home and disappears within few hours. You will have to find out, what is it that she is allergic to. You might have to find out this with respect to, her clothes, any painiting in the daycare, her bag, her friends things, her teacher's things, etc. I would also recommend you to see your pediatrician
in case, you do not find any allergen. It will be better if he can see the rash. It will help him in the diagnosis. I hope you have a record of all the teachers and the non-teaching staff in your son's daycare.
I hope I have been successful in clarifying your doubts and I will be available to you for any further doubts. Take care and stay healthy.