1) If the skin lesions come up rapidly with constitutional symptoms like catarrh and fever especially in children, it's most likely a viral exanthem. Treat symptomatically. Don't be too quick to prescribe antibiotics.
I have had former interns call me to thank me profusely for all the dermatology learnt
"To cure sometimes, to relieve often, to comfort always".
In all...you must always aim to improve the QoL of the patient even if a complete cure cannot be achieved.