perioral dermatitis help

More than a year ago now I was diagnosed with perioral dermatitis and promptly prescribed the antibiotic oxytetracycline which has since worked wonders for it and kept it at bay. I was a little concerned when my doctor informed me that I might have to stay on it for quite some time due to a relapse I had when I tried coming off the stuff for a while, but was informed that it's quite common for some to have to take this treatment for up to five years and so wasn't too worried. But just this last week or so I've become very anxious as the bumps have mysteriously started appearing again, despite the fact that I'm still taking the oxytet, basically I'm wondering whether it's possible for the treatment to stop working after a time? It's not as huge an outbreak as before, just two small patches on my chin, but it's taking a very very long time to clear up and I'm scared it's only going to get worse. There's been one or two changes in my facial routine recently that might have triggered it but I've never have had a relapse like this before while on the tablets.