According to Medical News Today, lip twitches can be explained away simply by drinking too much caffeine. Like any other muscle twitches, stress and anxiety can be culprits too. This is due to the amount of tension being put on your muscles and nerves, as well as adrenaline rushes, per Calm Clinic.

Aside from your mental health and a caffeine-heavy diet, a twitch in your lip can also be a result of certain deficiencies. Medical News Today notes that low potassium is often a common cause for twitches, which can cause spasms and cramps in any muscle including the lips.

There are also particular medical conditions that effect the muscles in the face, including Bell's palsy and hemifacial spasms. Bell's palsy is categorized as a sudden weakness in facial muscles according to the Mayo Clinic, where its believed swelling and inflammation can cause one side of your face to droop. For most, the condition is temporary and can improve after a few weeks. But some may continue to have symptoms for the rest of their life.

A hemifacial spasm, on the other hand, is a chronic condition that causes involuntary face twitching due to "compressed facial nerves," per Cleveland Clinic. While there's no cure for this, symptoms can be eased by taking it easy (like getting enough sleep and lowering stress), as well as through medication, injections, or surgery.