The first step in treating conjunctivitis is to identify the cause of what is causing the conjunctivitis. The causes of conjunctivitis can be divided into two categories, infectious and non-infectious, depending on their different nature. (i) Infectious due to infection of the conjunctiva by pathogenic microorganisms. Non-infectious allergic inflammation caused by local or systemic allergic reactions is the most common. External physical and chemical factors such as light and various chemicals can also be causative factors. In case of infectious conjunctivitis: antibacterial or antiviral eye drops or eye ointment. Depending on the pathogenic diagnosis, choose the appropriate therapeutic drug. For example, levofloxacin eye solution, tobramycin eye solution and erythromycin eye ointment are available for bacterial infections, and acyclovir eye solution is available for viral infections. For non-infectious conjunctivitis, such as allergic conjunctivitis, do not abuse antibiotics, but use anti-allergic eye drops, such as sodium cromoglycate eye solution and flumetron eye solution. Therefore, treatment should be based on the specific cause.