A lot of what was said last week during the discussion of genuine lip infections would be valid for this ailment as well. For example, LFP cases seem to hit those breeds with droopy, sagging lower lips, like the St Bernard (the dog in the Beethoven movie), the Cocker Spaniel, the Boxer, and those huge monstrous dogs which starred in Cujo and Turner and Hooch.
I think what really happens is that the lips too often rub against the canine teeth from the upper jaw. This constant friction