Fluorouracil - How long do I need to leave flourouracil on my skin? Supposed to use it on my neck?

My doctor had me leave it on. Once you apply it the cream will do its job. As far as your neck and cleavage I would ask your dermatologist where it should be applied. Just know that after 10 days whereever you put it will be really painful. But the alternative of skin cancer outweighs the pain. It won't seem like that on days 10 to 20 though. Take daily photos. Have a good opinion and know that this is just temporary.