Answered by Ustadha Shazia Ahmad
Does licking the lips more than once invalidate the fast?
If one licks the lips once, and then immediately licks them again, this does invalidate one’s fast.
It says in the Reliance of the Traveller, i1.18:
“Each of the following things invalidates the day’s fast when one knows they are unlawful (A: during an obligatory fast) and remembers one is fasting (A: but does them deliberately anyway); and they obligate one to both make up the fast-day later and fast the remainder of that day:
11) swallowing saliva that has left the mouth, such as when threading a needle and one moistens the end of the thread, and then remoistens it, swallowing some of the saliva, that the thread had been previously wetted with;”
And Allah knows best.