Is conjunctivitis contagious?
Generally, "red eye" refers to conjunctivitis. Whether it is contagious depends on its specific type. If it is bacterial or viral conjunctivitis, it may be contagious; however, if it is allergic or chemical conjunctivitis, it usually is not contagious. If you experience any discomfort, timely medical attention is recommended. Detailed explanations are as follows:

Bacterial or viral conjunctivitis may involve pathogens that multiply extensively in the patient's eye and can be transmitted to others through contact. For example, after a patient rubs their eyes with their hands, pathogens may contaminate the hands. Then, shaking hands with others or touching shared objects may spread the pathogens to others.
Allergic or chemical conjunctivitis is caused by allergic reactions or irritation from chemical substances, rather than pathogen infection. Therefore, this type of conjunctivitis generally does not spread to others through contact.
In daily life, maintaining personal hygiene, avoiding sharing eye-related items with others, and keeping the environment clean can effectively prevent the occurrence of conjunctivitis.