Why does my lip keep trying to swell up?

About two weeks ago I had bronchitis. I’m recovered now and my energy levels are almost back to normal. The strange thing is that the night before the fever started, both of my lips swelled up. My wife called them “duck lips.” Now, about every five days, the left side of my upper lip swells up. But all I have to do when this happens is take a Benadryl tablet and half an hour later the lip returns to normal. Rinse, lather, repeat. Strangest thing I’ve ever seen. Any idea(s) what is going on here?

I had a thread on this about four years ago. You may find something useful there.

This doesn’t happen to me any more. No idea why it stopped and no idea why it ever happened.