Bacterial conjunctivitis

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 1, 2016
StartDiseasesBacterial conjunctivitis

Bacterial conjunctivitis, commonly referred to as pink eye, is a relatively common infection of the eye. It is typically self-limiting, meaning that it will clear up on its own within a week, but some patients may require medical treatment. Bacterial conjunctivitis is quite contagious, but good hygiene and proper eye care can prevent its spread.


Definition & Facts

Bacterial and viral conjunctivitis are the two most common types of conjunctivitis or pink eye, although allergies and irritants can also cause similar symptoms. In children, bacterial infection is the most common cause of pink eye, while viral infection is a more common cause of conjunctivitis in adults.

Bacterial conjunctivitis does not usually result in serious or permanent complications. However, severe cases can cause temporary or permanent vision impairment or lead to systemic infection if left untreated.

Recurrent or severe cases of pink eye could be a sign of a more serious health concern, so further testing may be needed to determine the cause of the infection so that it can be properly treated to prevent future occurrences or complications.

Symptoms & Complaints

Symptoms of bacterial conjunctivitis can be present in one or both eyes, or they can start in one eye and later spread to the other.

The most common and easily identifiable symptom of bacterial conjunctivitis is the telltale redness or pinkness of the sclera, which is the white part of the eyeball.

Bacterial conjunctivitis causes a thick yellow or white pus-like discharge from the affected eye. Other symptoms may include mild to moderate swelling and redness of the upper and lower eyelids along with a burning or gritty feeling in the eye (but not sharp or stabbing pain).

Excess discharge can collect on the outside of the eyelids and harden when it dries, making it difficult to open the eye in the morning upon waking. Some more severe cases of bacterial conjunctivitis can also include a mild sensitivity or aversion to bright light, and the discharge can cause a temporary blurring of the vision that clears up when the discharge is wiped away from the eye.


Bacterial conjunctivitis is caused when bacteria is introduced into the eye. The bacteria then multiplies and causes irritation and inflammation of the conjunctiva, which is the thin, transparent lining that covers the white part of the eye and lines the eyelids.

This bacteria can be introduced into the eye from an ear infection (otitis) or sinus infection, or it can be introduced by touching the eye with unwashed hands or by close contact with a person who has an active infection.

Pink eye can also be spread by sharing cosmetic products such as mascara and eye liner with a person who has a current infection, or by using eye cosmetics that are expired.

The three most common bacteria that can cause conjunctivitis are Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenza. Chlamydia trachomatis can also cause bacterial conjunctivitis, although this type of infection is less common than other types. 

Diagnosis & Tests

A doctor can take a swab of the discharge to run a culture test in order to confirm a diagnosis of bacterial conjunctivitis. However, this is not necessary for most patients except in cases of recurrent pink eye, or if the patient’s symptoms do not respond to initial treatment. A doctor can usually make an accurate diagnosis by carefully investigating the patient’s symptoms.

Treatment & Therapy

Bacterial conjunctivitis will typically clear up on its own within a week without any kind of medical intervention. Good eye hygiene is crucial in the healing process. Cleaning the affected eyelid gently with a clean cloth soaked in warm water several times a day will help prevent the buildup of crusty discharge and remove bacteria and infected pus from the eye.

Contact lenses should be avoided until the eye is completely healed to prevent further irritation and recurrent infection. It is important to keep from touching the eye and to sanitize all cloths used to clean the eyelid to keep from re-infecting the patient or spreading the infection to others.

Antibiotic eye drops or ointment can speed healing and shorten the amount of time that the patient is contagious. Oral antibiotics are generally not prescribed for conjunctivitis, but may be prescribed if the conjunctivitis is caused by a sinus or ear infection. Viral pink eye will not respond to antibiotics.

Bacterial conjunctivitis accounts for only about 30 percent of all cases of pink eye, yet antibiotics are prescribed for nearly 80 percent of patients complaining of pink eye. Recurrent or antibiotic-resistant infections may need more aggressive treatment. 

Prevention & Prophylaxis

Good eye hygiene is key in preventing bacterial infections. Regular hand washing is the single most important step in preventing the contraction and spread of bacterial conjunctivitis.

People who use contact lenses should be sure to wash their hands well before inserting and removing contacts, and be sure to carefully follow manufacturer instructions in caring for contact lenses.

Disposable contacts should be disposed of promptly, and reusable contacts should be kept clean. It is advisable to stay away from people who have an active conjunctivitis infection, and people who currently have pink eye should stay home and away from other people if at all possible to keep from spreading it to others.