Blepharitis, inflammation of the lid margin, may be caused by a bacterial infection, commonly Staphylococcus. Crusts appear at the base of the eyelashes, along with erythema (redness) and in severe cases corneal ulcers. Bacterial blepharitis is treated with topical antibiotics and lid washes with a nonburning baby shampoo.

Another cause of blepharitis is a louse infestation (Phthirus pubis). Use of a magnifying glass allows visualization of nits and adult lice on the eyelashes. Removal of the parasites and topical application of phospholine iodide or 1% mercuric oxide is the recommended treatment.

A localized infection of the sebaceous glands of the eyelid (hordeolum) produces red, painful, localized swelling, whereas a localized infection of the oil-secreting glands of the eyelid (chalazion) produces a painless localized swelling on the eyelid.

Conjunctivitis in the newborn (ophthalmia neonatorum) may occur during the first 4 weeks of age and presents as redness, swelling, and discharge of the eyelids and conjunctiva. Common causes of ophthalmia neonatorum include silver nitrate drops used at birth, viral infection (herpes simplex), or bacterial infection (gonococcal, staphylococcal, or chlamydial). If caused by Neisseria gonorrhoeae vision loss may occur. It is important to note that silver nitrate drops do not protect the infant from acquiring a chlamydia infection during a vaginal birth. Treatment is achieved by specific antibiotics that target the responsible organism.

The conjunctiva, which lines the posterior surface of the eyelids and anterior surface of the cornea, is a thin transparent mucous membrane. When this area becomes inflamed in response to exposure to viruses, bacteria, chemicals, or allergens it is called conjunctivitis. Bacterial conjunctivitis, which produces a purulent discharge, may affect one or both eyes, may be caused by a local or systemic infection, and is highly contagious. Bacteria commonly responsible for the infection include Staphylococcus aureus, Bartonella henselae (responsible for cat-scratch fever) and Haemophilus. Children and adolescents who do not care for their contact lenses properly are at risk for developing bacterial conjunctivitis. Infections are treated by the application of topical antibiotics or systemic antibiotics if the causative pathogen is Chlamydia trachomatis, N. gonorrhoeae, or Neisseria meningitides.