The symptoms of Bell's palsy are likely to come on very quickly, often in a matter of hours or overnight, and there may be some sudden pain around the ear. Symptoms can also start more gradually. The main symptom is likely to be paralysis or weakness on one side of the face, along with a sagging eyebrow and difficulty closing the eye. There are several other possible symptoms:

• Numbness of the face
• Difficulty in speaking
• Loss of taste in the front portion of the tongue
• Dryness or watering of the affected eye, and a turned out lower eyelid.
• Dribbling when drinking or after cleaning teeth
• Ear pain (especially below the ear)
• Intolerance to loud noises on the affected side.

Rarely, new nerve fibres that grow back after paralysis connect to the wrong facial muscle. This can result in lasting damage, and cause one or several of the following:

• Blinking when attempting to smile
• Involuntary movement of the corners of the mouth when closing the eyes
• Twitching
• Facial spasms
• The formation of false "crocodile" tears at the same time as saliva.

Bell's palsy is a peripheral (affecting the peripheral rather than the central nervous system) facial paralysis that results from damage to the seventh cranial nerve, or "facial nerve."

In traditional Chinese medicine, this condition is due to pathogenic wind-cold attacking the Shaoyang (Liver, Gall Bladder) and Yangming (Stomach, Large Intestine) channels as well as the tendons and muscles. This can occur when a patient is exposed to wind (e.g.sleeping near an open window, driving with the windows down, going on a boat when the winds are strong) and is more common in the spring and autumn months.

Often people with Bell's palsy have a deficient immune system (possibly due to genetics, unresolved or chronic illness, improper diet, rest, exposure to toxic chemicals or drugs, or undue physical and emotional stress). As a result, they are more vulnerable to outside sources such as further exposure to physical and emotional stress factors or viral and bacterial pathogens. The exposure to the external source causes the immune system to produce an inflammatory response in the affected region resulting in swelling of the surrounding tissues. This swelling can then obstruct the normal function of the nerves and vessels (ie. the facial nerve). As a result, there is an obstruction of "Qi," (pronounced "chee") (vital energy) and blood in these areas that leads to malnourishment of the tendons and muscles and thus a propensity for the facial muscles to become lax or paralyzed. The lack of nourishment to the local area can therefore cause symptoms of numbness and tingling, which are common signs of Qi and/or blood deficiency in TCM (Traditional Chinese Medicine).