Table 1.

Characteristics of different types of conjunctivitis

Characteristic	Bacterial conjunctivitis	Viral conjunctivitis	Allergic conjunctivitis
Discharge	Thick, purulent, yellow	Watery	Watery
Sensation	Gritty	Gritty	Itchy
Affected eyes	One at first, commonly spreads to other after initial infection of first eye	One at first, commonly spreads to other after initial infection of first eye	Both eyes
Associated symptoms	Nil	Recent signs and symptoms of an upper respiratory tract infection	May be associated with a personal or family history of allergic rhinitis or atopy (eczema, asthma)
Pathology	Infection with bacterial organism (commonly Staphylococcus aureus, Streptococcus pneumoniae)	Infection with a virus such as adenovirus (most common) or herpes simplex	Exposure to allergens such as animal dander, dust mites, pollen
Contagious	Highly	Highly (if adenovirus infection)	No