What Causes Reddish Bumps With Burning Sensation On The Upper Lips?

My daughter has been complaining about her upper lip -- she has little red bumps for almost a year now and every couple of months they begin to burn extremely badly. The burning sensation is accompanied by the bumps getting bigger. It stays that way for about 2 weeks with terrible burning and then the bumps get smaller. Then the cycle continues. Our internist thought it was cold sores but they don t go away. Our dermatologist thought it was pimples and she prescribed a retinol cream that made it hurt even more. She then told us to discontinue the cream and use a mild toothpaste, but it still hurts. Any ideas?