Advice ladies

So yesterday around 3 she had a small red area on her face and then I noticed it was on her arms. I took her pjs off and told her dad if it gets worse we are taking her in to urgent care. Well in a few minutes was all it took so we took her in. They said it was an allergic reaction to something she touched. We didn’t do anything new or different yesterday. They gave her Benadryl and she was all clear by last nights. Woke up this morning it’s now on her legs and one arm again. Any ideas? I’m calling the doctor tomorrow!