Causes of numb lips include allergic reactions, medication side effects and neuropathy, according to Healthgrades. Some people may experience numb lips after receiving an anesthetic at the dentist or as a response to cold temperatures.
Neuropathy is nerve damage that can affect the lips, reports Healthgrades. Lack of muscle control in the lips would be an additional symptom of neuropathy. Some diseases can cause this nerve damage, as well as nutritional deficiencies or exposure to toxins. If other symptoms such as swelling or trouble breathing are occurring in addition to numb limps, it can be a severe allergic reaction, and it is important to contact a doctor.