Fixed drug eruption. More cases of fde?

My daughter 3 years old.. suddenly out of the blue she had a rashes all over her body.. on June mid this year.. it's gone after few doses of citrizen .. bu from that day only one place under her left arm a dark pigmentation stayed as such.. I recently visited dermatologist he said it may be fde for some medication.. find the cause and drop it.. she catches cold easily.. so her frequent medication are montair, paracetamol 250, ascoril ls, and cefaclar OR distaclear,.. So which one causes more cases of fde? If it is para or antibiotic , can I fine a alternative Since she catches cold on montly basis. P.s : how come after three years she suddenly become allergic to these medication since I am using for very long time. Thank you for your time