Daughter has skin colored bumpy itchy rash spreading on body tried betaderm & aquaphor. not working. allergy meds don't help either. what could it be?

Need to see a rash: There is really is no way to tell what a rash is without seeing it. Could be a contact dermatitis, eczema,a reaction to the Biaxin or scabes. Hydrocortisone and Benadryl (diphenhydramine) help with itching, but probably needs to be seen to diagnose.

Pityriasis?: There are several inflammatory rashes that appear frequently in children and a proper diagnosis is helpful in not only giving the right treatment but avoiding unnecessary treatment. In the derm word, a picture is indeed better than a thousand word. The rash could be eczema,requiring steroid cream. For the other common rash, see link.