Can you help me identify the cause of the one red eye in this picture?

The cause of the one red eye in the picture could be due to a condition called conjunctivitis, also known as pink eye. This is an inflammation of the outer layer of the eye and inner surface of the eyelid. It can be caused by a viral or bacterial infection, Allergies, or irritants. It is important to consult a healthcare professional for proper diagnosis and treatment.