Viruses are the most common cause of conjunctivitis, and both viral and bacterial causes may accompany respiratory ailments, such as colds, sore throats, or the flu. You can spread viral and bacterial pink eye through both direct and indirect contact with others, through contact with the fluid that drains from an infected eye.
Conjunctivitis may also occur due to allergies. This could be in response to contact with some types of pollen, for example, that stimulates histamine production. This can cause itchy eyes and in extreme cases, pink eye. Typically, allergy-related pink eye is accompanied by sneezing, runny nose, and other common allergy responses.
You may also develop pink eye due to chemical irritation or a foreign object in your eye. Depending on the severity of the irritant, urgent eye care may be advised to prevent permanent damage.