Eye Infections

DISCLAIMER: The content of this Website is not influenced by sponsors. The information contained herein should NOT be used as a substitute for the advice of an appropriately qualified and licensed physician or other health care provider. The information provided here is for educational and informational purposes only. In no way should it be considered as offering medical advice. Please check with a physician if you suspect you are ill.



Conjunctivitis is a common medical condition. It is the most likely diagnosis in a patient with a red eye and drainage.


New-onset conjunctivitis is usually not very harmful, it is a condition that will usually go away on its own or can be easily treated. Your doctor will need to ensure that the red eye is not due to a more serious medical condition that could threaten your eye sight such as, new-onset glaucoma, iritis, and infectious keratitis. These medical conditions would need to be evaluated and managed by an eye specialist, an ophthalmologist.


Conjunctivitis literally means "inflammation of the conjunctiva." The conjunctiva is wet outer surface of the inner eye lids and the surface of the eye balls.


The conjunctiva is generally transparent. When it is inflamed, as in conjunctivitis, it looks pink or red at a distance. Up close can see fine, intact, blood vessels. All conjunctivitis will have a red eye, but not all red eyes are conjunctivitis.




New-onset conjunctivitis can be due to infectious or non-infectious causes:



- Bacterial

- Viral



- Allergic

- Nonallergic


The most common cause of conjunctivitis is different in children and adults. Bacterial conjunctivitis is more common in children than in adults. Overall viral conjunctivitis is more common but children with bacterial infections are more likely to visit their doctor.  Most infectious causes of conjunctivitis are viral in both adults and children.


Bacterial conjunctivitis 

Bacterial conjunctivitis is commonly caused by Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. S. aureus infections are common in adults; the other organisms are more common in children.


Bacterial conjunctivitis is spread by direct contact from a patient and his or her secretions or through contaminated objects and surfaces. It is highly contagious.


Patients with bacterial conjunctivitis typically will have redness and discharge in one eye, although it can also be present in both eyes. Similar to viral and allergic conjunctivitis, the eye involved will often be "closed shut" in the morning.


The pus discharge will continue throughout the day. The discharge is thick and mucus-like; it may be yellow, white, or green. The appearance is different from that of viral or allergic conjunctivitis, which often presents with a mostly watery discharge during the day, with a scanty, stringy component that is mucus rather than pus.


On examination, the patient with bacterial conjunctivitis typically will have pus discharge over the outer portion of the eye lid and in the corners of the eye. More pus discharge will appear within minutes of wiping the lids. This is opposite to patients with viral or allergic conjunctivitis, in whom the eyes appear watery, there may be mucus present on close inspection or if one pulls down the lower lid, but pus does not appear spontaneously and continuously at the edge of the eye lid and in the corners of the eye.


A bacterial called Neisseria, especially N. gonorrhea, can cause a very serious bacterial conjunctivitis that can threaten eye sight and requires an immediate referral to an ophthalmologist. The infection is usually contracted from the genitalia region and spread to the hands and then to the eyes. Painful urination is typically also present.


Infection with Neisseria will cause a profuse, thick, pus-filled discharge within 12 hours of infection; the amount of discharge is impressive. Other symptoms will also develop rapidly, such as, redness, irritation, and tenderness with light pressure. There is typically significant redness and swelling of the eye ball, eye lid swelling, and tender lymph nodes located over the front of the ears. These patients will require hospitalization for IV and topical antibiotics.


Viral conjunctivitis 

Viral conjunctivitis is typically caused by adenovirus. The conjunctivitis may be part of a viral precursor where later lymph node enlargement, fever, sore throat, and a upper respiratory tract infection will develop; the eye infection can also be the only outward symptom of the disease. Viral conjunctivitis is highly contagious; it is spread by direct contact with the patient and his or her secretions or with contaminated objects and surfaces.


Patients with viral conjunctivitis typically will have red, dilated, eye blood vessels, watery or mucus-like discharge, and a burning, sandy, or gritty feeling in one eye. Patients may say that they have "pus" in the eye, but on further questioning it will only be dried discharge present in the morning followed by a watery discharge, with a little bit of mucus discharge throughout the day.


The opposite eye will usually become involved within 24 to 48 hours.


On examination of the eye there typically is only mucus-like discharge when the lower lid is pulled down or only in the corner of the eye. Usually there is profuse tearing present and not discharge. The inner portion of the eyelid near the nose may have a bumpy appearance. There may be an enlarged and tender lymph node in front of the ears.


Viral conjunctivitis will go away on its own. This is similar to the common cold. While recovery can begin within days, the symptoms will frequently get worse for the first three to five days, with very gradual improvement over the following one to two weeks for a total duration of two to three weeks.


Similar to how a person that has recently gotten over a cold might continue to have morning coughing and nasal congestion or discharge two weeks after symptoms first come on, patients with viral conjunctivitis may have dried secretions in the morning two weeks after the initial symptoms, although the daytime redness, irritation, and tearing should be much improved.



Keratoconjunctivitis is a form of viral conjunctivitis. It can cause significant inflammation to the outer aspect of the eye, in addition to conjunctivitis. It is typically caused by adenovirus (similar to the less severe viral conjunctivitis discussed above). In addition to the typical symptoms of viral conjunctivitis, the patient will develop a foreign body sensation along with multiple small bumps over the outer portion of the eye, barely visible with a penlight. The foreign body sensation is severe enough to prevent opening the eyes, and the bumps will typically affect the vision.


Keratitis is a potentially vision-threatening condition; therefore patients with this condition should be referred to an ophthalmologist to confirm the diagnosis and to decide if treatment with topical steroids is needed.


Allergic conjunctivitis 

Allergic conjunctivitis is caused by allergens floating within the air coming in contact with the eye. This contact results in inflammation. It typically comes on as redness throughout both eyes, watery discharge, and itching. Itching is the main symptom of eye allergies, separating it from a viral infection, which is more typically described as grittiness, burning, or irritation. Eye rubbing can worsen symptoms. Patients with allergic conjunctivitis often have a history of an eczema-like skin rash, seasonal allergies, or a specific allergy (eg, to cats).


Similar to viral conjunctivitis, allergic conjunctivitis causes enlarged blood vessels throughout the eye with a bumpy appearance to the inner eyelid near the nose and profuse watery or a mucus-like discharge. There may be dried secretions in the morning. The history of itching, allergies or hay fever is the main symptom that separates allergic and viral conjunctivitis; the appearance of both are very similar.


In some cases of allergic conjunctivitis, there is significant redness and swelling; in extreme cases, the swelling can be so significant that it causes the outer portion of the eye to bulge-out, extending forward beyond the edge of the  eyelid. The is most commonly seen in patients with extreme allergy to cats.


Noninfectious, nonallergic conjunctivitis 

Patients can develop a red eye and discharge that is not related to an infectious or inflammatory process. The discharge is more likely mucus than pus. Usually the cause is due to dryness or contact with an irritating chemical.


Patients with dry eyes may report long-term, or occasional, redness or discharge and may think that it is caused by an infection.


Patients whose eyes are irrigated after a chemical splash may have redness and discharge; this is often related to irrigating the eye rather than a resulting infection.


A patient with a foreign body in the eye, where the foreign body has subsequently fallen out, may have redness and discharge for 12 to 24 hours after the injury.


All of these causes should generally improve on their own within 24 hours.


Chlamydia infections

In developing countries, Chlamydia is a major cause of eye disorders and blindness.


Chlamydia can also cause a long-term, slowly developing, conjunctivitis. The infection is sexually transmitted. Commonly a patient will also have a genital Chlamydia infection that does not cause any symptoms.


The eye infection can affect one or both eyes. It can last weeks to months and will not respond to topical antibiotic treatment.




Conjunctivitis is a diagnosis that is made when all other more serious causes of eye infections have been ruled-out. The diagnosis can be made in a patient with a red eye and discharge only if the vision is normal and there is no evidence of more serious condition such as, keratitis, iritis, or glaucoma.


Patients with all types of conjunctivitis will reports having morning build-up of dried discharge and daytime redness and discharge. On examination, there should be no abnormalities of the eyelids such as a stye, an ulcer, or inflammation of the eyelids.


The redness in conjunctivitis should be widespread, involving the outer layer of the eyeballs and the inner surface of the eyelids. Other conditions such as, retained foreign bodies, an abnormal appearing growth over the outside of the eye (pterygium), or a distinct triangular area of dilated blood vessels (episcleritis) should be considered if the dilated blood vessels occur in only one location rather than a spread-out distribution over the entire eye.


The serious conditions that cause a red eye such as, keratitis, iritis, and glaucoma, will involve the entire outer aspect of the eye, but will spare the inner aspect of the lower eyelid near the nose.


Cultures are not necessary for the initial diagnosis and treatment of conjunctivitis. The exception is in patients where Neisseria gonorrhea is suspected.


A rapid (10 minute) test for adenoviral conjunctivitis is now available. As discussed above, adenovirus is the major cause of viral conjunctivitis and likely accounts for a significant number of doctor visits for conjunctivitis. This test can avoid unnecessary use of antibiotics.


Contact lens wearers 

The diagnosis of conjunctivitis should be made carefully in contact lens wearers, who are at risk for developing chronic conjunctivitis that will require a change in contact lens fit, lens type, or lens hygiene, and may require long-term treatment measures.


 Soft contact lens wearers have a high risk of an infection caused by pseudomonas, especially with use of extended-wear lenses. This causes a sudden-onset red eye and discharge along with an ulcer and inflammation. The ulcer can lead to permanent vision loss within 24 hours if it is not recognized and treated appropriately. For this reason, the presence of keratitis should be ruled out prior to assuming and treating conjunctivitis. Keratitis causes a foreign body sensation, and the patient is usually unable to open their eyes on their own or keep it open; there is typically a white film over the outside of the eye visible with a pen light.


A contact lens wearer with an sudden-onset red eye and discharge should be advised to discontinue use of their contact lenses immediately and they should be seen by an eye care provider if the symptoms do not improve within 12 to 24 hours. The patient may be treated for acute conjunctivitis only if there is no evidence of keratitis.


Chronic conjunctivitis will need to be managed by a knowledgeable optometrist/ophthalmologist team.


Signs that a serious visual problem may be present include:

-A change in vision

-Sensitivity to light

-Severe foreign body sensation that prevents a patient from keeping their eye open

-A white film over the outside of the eye

-A pupil that does not change its size when light is shined upon it

-Severe headache with nausea

-Dilated blood vessels around the periphery of the colored part of the eye (iris)




Viral, allergic, and other causes of conjunctivitis are all conditions that will get better on their own without any specific treatments. Medication can be used to improve symptoms but will do nothing to change the duration of the infection. Bacterial conjunctivitis will also likely go away on its own in most cases, although treatment will probably shorten the course and reduce person-to-person spread.


Therapy should be targeted at the cause of conjunctivitis suggested by the history and examination.



Appropriate choices for bacterial conjunctivitis include antibiotics such as erythromycin eye ointment, sulfa eye drops, or polymyxin/trimethoprim drops. The dose is 1/2 inch (1.25 cm) of ointment applied inside the lower lid or 1 to 2 drops applied four times daily for five to seven days. It is reasonable to decrease the dose from four times daily to twice daily, if there is improvement in symptoms after a few days.


These antibiotics are effective against most common infections responsible for bacterial conjunctivitis, and patients should respond to this treatment within one to two days by showing a decrease in discharge, redness, and irritation. Patients who do not respond should be referred to an ophthalmologist.


Ointment is preferred over drops for children, those with poor compliance, or those in whom it is difficult to administer eye medications. Ointment will remain on the lids and will continue to be effective even if it is not clear that any of the medication reached the outside of the eye. Because ointments blur vision for 20 minutes after the medication is applied, drops are preferable for most adults who need to read, drive, and perform other tasks that require clear vision immediately after the medication is applied.


Alternative medication include bacitracin ointment, sulfacetamide ointment, polymyxin-bacitracin ointment, fluoroquinolone drops, or azithromycin drops. Aminoglycoside drops and ointments are poor choices since they are toxic to the outside of the eye and can cause serious inflammation to the outside of the eye after several days of use.


The fluoroquinolones are effective and well-tolerated; they are the preferred treatment for corneal ulcers and are extremely effective against pseudomonas.  However, fluoroquinolones should not be the first choice used for routine cases of bacterial conjunctivitis because of concerns of causing resistance and high cost. The exception is conjunctivitis in a contact lens wearer; once keratitis has been ruled-out, it is reasonable to treat these individuals with a fluoroquinolone antibiotic due to the high likelihood of a pseudomonas infection.


Azithromycin is a liquid antibiotic for bacterial conjunctivitis and can be used in patients one year of age and older. It can be given less frequently, as compared to other eye drop antibiotics, only 1 drop twice daily for two days, then one drop daily for five days, but it is also considerably more expensive than erythromycin or sulfacetamide.


As mentioned above, any contact lens wearer with a red eye should discontinue contact lens wear. If the diagnosis is conjunctivitis, patients can go back to wearing their contact lenses when the eye is white and has no discharge for 24 hours after the treatment with antibiotic is complete. The lens case should be thrown out and the lenses should be disinfected overnight or replaced if disposable.



There is no specific antiviral medication for the treatment of viral conjunctivitis. Some patients may get some relief from topical antihistamine/decongestants. These are available over-the-counter (Naphcon-A® or Ocuhist®). These medications will treat the symptoms of viral conjunctivitis but not the disease, just as common cold medication treat the symptoms rather than the cause of a cold. Warm or cool compresses with a water soaked washcloth may provide additional symptom relief.


Some doctors will prescribe antibiotic ointments for viral conjunctivitis to provide moisture relief to the eyes. A better solution would be to use non-antibiotic lubricating drops instead.


Patients should be aware that the irritation and discharge may get worse for three to five days before getting better, that symptoms can persist for two to three weeks, and that use of any topical medication for that length of time might result in irritation and damage to the eye, which can itself cause redness and discharge.


Doctors should avoid using one agent after another in patients with viral conjunctivitis who are expecting a quick-f ix to their symptoms.


Inclusion conjunctivitis 

Diagnosis can be confirmed with laboratory testing. Antibiotics taken by mouth or IV is required to treat the infection. Treatment is typically with antibiotics such as, doxycycline, tetracycline, erythromycin, or azithromycin.


Allergic conjunctivitis 

There are many medications available for allergic conjunctivitis, both over-the-counter and by prescription.


Non-infectious and non-allergic treatments 

The outer surface of the eye will regenerate rapidly from injuries that lead to a conjunctivitis and the injury should eventually get better on its own. Even so, some patients may feel better more quickly with the use of topical lubricants, which can be purchased over-the-counter as drops and ointments. Preservative-free preparations are more expensive and are necessary only in severe cases of dry eye or in highly allergic patients.


Lubricant drops can be used as often as hourly with no side effects. The ointment provides longer lasting relief but blurs vision; for this reason, many patients use the ointment only at bedtime. It may be a good idea to switch brands if you have found one brand of drop or ointment to be irritating since each preparation contains different active ingredients, methods of delivery, and preservatives.


Treating with antibiotics

Doctors often feel pressured to prescribe antibiotics for conjunctivitis, even when it appears to be a viral infection. This can be a particular issue for parents because most daycare centers and schools require that students with conjunctivitis receive 24 hours of topical antibiotics before returning school.


If the decision is made to treat the infection presumptively with antibiotics, experts recommend using inexpensive nontoxic antibiotic such as erythromycin eye ointment or sulfa eye drops (except in the case of contact lens wearers). Ointment is preferred over drops for children.


Steroid use  

Topical steroids have no role in the treatment of new-onset conjunctivitis. Their use can threaten eye sight by causing scarring, melting, and perforation, of the outer eye when used incorrectly in herpes of the eye or bacterial keratitis, both of which cause a red eye and discharge.


Long-term use of topical steroids can also cause cataracts and glaucoma. Ophthalmologists may prescribe steroids in certain cases of eye allergy, viral keratitis, and chronic eyelid inflammation.


Poor response 

Patients with new-onset bacterial conjunctivitis should respond to treatment within one to two days by showing a decrease in discharge, redness, and irritation. Patients who do not respond should be referred to an ophthalmologist. Patients with other forms of acute conjunctivitis should respond within two weeks, and those who do not should also be referred to an ophthalmologist.


Other medical conditions should be considered in patients who do not respond to treatment, such as, dry eyes, a topical drug reaction, tissue growth over the outer eyeball (pterygium), inflammation of the outer eyelid and eye, and inclusion conjunctivitis.


Returning To Work or School


Bacterial and viral conjunctivitis are both highly contagious and spread by direct contact with secretions or contact with contaminated objects. People who have an infection should not share handkerchiefs, tissues, towels, makeup, linens, or silverware. The way to prevent spread of the disease to others is to stay home until there is no longer any discharge.


Most daycare centers and schools require that students receive 24 hours of topical antibiotics before returning to school. This treatment is effective against bacterial infections but will do nothing to decrease the spread of viral infections.


Patients should treat their infection a common cold, and their decision to return to work or school should be similar to the one they would make in that situation. Those who have contact with the very old, the very young, and people with weak immune systems should take care to avoid spread of infection from their eye secretions to these at risk people.