What should I do as a basic care routine when I have dermatitis?

My dermatitis, which had been on and off for a while, has finally returned. I've occasionally had mild early symptoms of dermatitis over the past few months, but they never got worse and usually cleared up quickly. So I let my guard down. I think I irritated my skin too much when I washed my face, and it started stinging and itching. I hoped it would go away, but it persisted for a few days, and when I woke up yesterday morning, I had millet-sized blisters all over my mouth...ㅠㅠ I went to a dermatologist near my office during lunch, took some prescription medication, and applied steroid ointment. Today, the itchiness has eased a bit, but my skin feels incredibly tight. The doctor told me to only use lotion, so I've been using Cetaphil lotion. But my skin feels hot, and the surface is thin and dry, like plastic. The lotion alone feels like it's going to tear. What should I do to treat this? Can I just apply some oily cream?