Bell's Palsy: This is the most common cause of unilateral facial palsy in children, characterized by sudden onset of weakness or paralysis of the facial muscles on one side of the face. It is often associated with viral infections and typically has a good prognosis with prompt treatment.

Lyme Disease: Caused by the bacterium Borrelia burgdorferi, transmitted by tick bites. Facial palsy can be an early manifestation, especially in endemic areas.
Varicella-Zoster Virus (VZV) Infection: Reactivation of VZV can cause Ramsay Hunt syndrome type 2, leading to facial palsy, ear pain, and vesicles in the ear.
Trauma: Direct injury to the facial nerve can result in facial palsy, which could be due to accidents, falls, or even birth trauma in younger children.

Brain Tumors (e.g., Acoustic Neuroma, Pontine Glioma): Although rare, these can compress the facial nerve, leading to palsy. Early detection is crucial for treatment and prognosis.
Meningitis: Inflammation of the protective membranes covering the brain and spinal cord can cause facial nerve palsy among other symptoms like fever, headache, and stiff neck.
Stroke: Though uncommon in children, a stroke can cause facial weakness or palsy and is a medical emergency.

Moebius Syndrome: A rare neurological disorder characterized by facial paralysis and impaired eye movement, present at birth.
Melkersson-Rosenthal Syndrome: A rare neurological disorder characterized by recurrent, often unilateral, facial paralysis or weakness, along with swelling of the face and lips, and the development of folds and furrows in the tongue (fissured tongue).
Sarcoidosis: A condition in which inflammatory cells form lumps known as granulomas in various parts of the body, including the nerves, leading to facial palsy among other symptoms.
Guillain-Barré Syndrome: An autoimmune disorder where the body's immune system mistakenly attacks part of its peripheral nervous system, which can lead to muscle weakness, and sometimes facial palsy, among other symptoms.