After we have Bells Palsy it is very normal for some of us to get regressive symptoms occasionally. When we are going through a period of stress, lacking sleep, have been unwell or have generally been overdoing things, our faces can react badly.
This doesn't mean we are getting BP again, it simply means that we need to cut the stress, get some rest and take life a little slower for a few days. Our faces become our early warning system (stressometer) and we should listen to them. A few days of taking care of ourselves and things are usually back to normal, but if not and you develop paralysis you should see your doctor immediately.