Toilet Bowl seal leak

Just had that problem ,the seal is nearly six years old, and starting leaking ,not holding water in the bowl, cleaned it well with a round bristle brush about the same size in diameter as the the opening, and then with rubber gloves on put a coat of vaseline around inside and outside of the rubber seal, been working fine for the past six weeks. Before it would not hold water for two minutes. I think the key is a good cleaning of the seal itself, which probably does not get cleaned as well as it should with normal cleaning. Anyway it worked for us.