Bell's palsy :
The sudden development of muscle weakness on one side of the face is called Bell's palsy. The reason behind this is damage to the seventh cranial nerve which is the facial nerve. Even though Bell's palsy can happen at any age, it is less common before age 15 and after age 60.
People at risk of developing Bell's palsy are those who have diabetes, influenza or cold, upper respiratory disorder, or in pregnant women. Some of the common symptoms associated with this condition are loss of sensation in the face, headache, drooling, squinting, blinking, etc.