There are different types of conjunctivitis. The most common types of conjunctivitis are viral conjunctivitis, bacterial conjunctivitis, and allergic conjunctivitis. There are five kinds of allergic conjunctivitis.

The most common type of conjunctivitis is bacterial conjunctivitis. Bacterial conjunctivitis is caused by a bacterial infection of the conjunctiva which is the outer membrane of the eye and underside of the eyelid. Bacterial conjunctivitis often causes thick, yellowish discharge and redness of the eye. Bacterial conjunctivitis is highly contagious.

Viral conjunctivitis is caused by a viral infection. Viral conjunctivitis is contagious. Most cases of viral conjunctivitis are allowed to run their course. Viral conjunctivitis may cause a pink or reddish discoloration of the whites of the eyes, itchiness, pain, watery discharge, and the sensation that there is something in the eye. Some may experience a mild sensitivity to light. The symptoms usually subside within ten days.

Allergic conjunctivitis is caused by exposure to allergens or irritants. Eyes with allergic conjunctivitis may appear pink or red and be itchy and watery. Antihistamines often help clear up the symptoms. Allergic conjunctivitis is not contagious. The kinds of allergic conjunctivitis are seasonal allergic conjunctivitis, perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis, and giant papillary conjunctivitis. Allergic conjunctivitis can last longer than other forms of conjunctivitis, especially if there is ongoing exposure to the allergen.

Giant papillary conjunctivitis is a type of allergic conjunctivitis that causes redness of the eye and eyelid and swelling of the eyelid and lesions or swollen bumps on the underside of the eyelid. This condition can cause sensitivity to light, itchiness, burning sensations, and discharge from the eyes. Giant papillary conjunctivitis is often caused by an allergic reaction to an irritant on the eye such as sutures from surgery, a damaged contact lens, a prosthetic eye, or a dirty contact lens.

Seasonal conjunctivitis is caused by seasonal allergens in the environment such as ragweed or hay fever. Perennial allergic conjunctivitis is caused by allergens that are present in the environment all year round. Common perennial allergens are dust mites, pet dander, and mold which can be both perennial and seasonal. Another type of allergic conjunctivitis is atopic keratonconjunctivitis. Atopic keratoconjunctivitis is associated with atopic dermatitis, the most common type of eczema.

Neonatal conjunctivitis is conjunctivitis that is contracted during birth. This type of pink eye can be viral or bacterial and is caused by sexually transmitted diseases of the baby’s mother. During the birth, the baby is exposed to the sexually transmitted disease. Neonatal conjunctivitis can be very serious and can lead to blindness. Common sexually transmitted diseases that cause neonatal conjunctivitis are gonorrhea, Chlamydia, and herpes.