Is ablution valid with dry skin flakes on the lips that may fall off during ablution or remain attached?

The presence of dry skin on the lips does not affect the validity of ablution (wudu') as long as water reaches beneath it, especially if the flakes are hanging loose. As for attached flakes, there is no need to peel them off; rather, they should be washed along with the outer surface of the lips. If any part of them falls off during ablution, the spot where it fell must be washed. What is obligatory to wash from the lips during ablution is only their outer surface, meaning what is visible when they are naturally closed. As for what is concealed inside the mouth, it is not obligatory to wash it.