bell's palsy is s temporary facial paralysis resulting from damage or trauma to facial nerve which is called the 7th cranial nerve which travels through a bony canal called the fallopian canal to reach the muscles which it supplied.
bell's palsy occurs when this nerve gets swollen, inflammed or compressed resulting in facial weakness or paralysis. but exactly what causes it is a topic of debate.
most scientists believe that herpes simplex is one cause. but bell's palsy is also seen associated with influenza, chronic middle ear infections, tumors, Lyme disease and trauma to the skull.
cold whether aggravates it.