A related discussion, blisters /open cut was started.
5-flourouracil can be irritating, but it can be used on the lips, under proper supervision. Your husband might want to speak to the dermatologist who prescribed it to get more details about what to do if it gets too drying, as well to speak about alternative approaches (one of which is to do nothing and watch, as the first doctor suggested.)
Best.
Dr. Rockoff