There are many common reasons for lip twitching, including stress or anxiety; fatigue; anger; or substance withdrawal, according to Dr. Chris from Health Hype. Irritation to the nerve may also be present in a noncommon cause of lip twitching.
In most cases, lip twitching is behind a nonserious cause. Stress; high anxiety; fatigue; strong emotions of anger or fear; or an intake of large amounts of caffeine may result in lip twitching ranging from a few minutes to a few days, explains Dr. Chris. However, if lip twitching does not clear up within a few days, the underlying cause may be serious, and the condition should be examined by a doctor.
Lip twitching occurs when there is an unexpected contraction of the lip muscles or the muscle fibers. Twitching can occur when the lips are at rest or after direct stimulation of the lips, causing an irritation or injury to the nerve. The lip may twitch rapidly and unpredictably after pressure or heat is applied to the nerve equipping the lips, according to Dr. Chris. Muscle fatigue is present in the lips when purposely extending or moving the lips in motion, which may cause twitching of either or both lips.