DS had one that wouldn't go away even with Hydrozole. Got Daktozin from the chemist which is thicker and used morning and night. Then used curash medicated powder during the day with lots of no nappy time.
I was battling antibiotic and teething poo at the same time and his poor bottom was so red and blistered. Within 2 days he was no longer screaming during nappy changes and after a week his bottom was perfect again