What Is Conjunctivitis?

Conjunctivitis, also known as pink eye, is the inflammation or infection of the conjunctiva, the transparent membrane that covers the white part of the eyeball and inner eyelid. Some forms (bacterial, viral) are highly contagious. Others may be triggered by an allergy or exposure to harsh chemicals. Symptoms include redness, itching, tearing, discharge, and more.

Because there are many different causes of conjunctivitis, it is important to see a healthcare provider to determine the appropriate treatment, which may include eye drops, oral medications, ointments, and/or comfort measures.

Types and Causes of Conjunctivitis

Pink eye is a fairly common condition with many possible causes. They can be classified into several types: viral conjunctivitis, bacterial conjunctivitis, allergic conjunctivitis, chemical conjunctivitis, and autoimmune/inflammatory conjunctivitis.

Viral Conjunctivitis

The most common viral type, which is highly contagious, is epidemic keratoconjunctivitis (EKC)— what most people are talking about when they refer to pink eye. Viral conjunctivitis can spread through hand-to-eye contact or contaminated objects.

Viral conjunctivitis can be linked to a number of viruses, including adenoviruses, the measles virus, and herpes simplex virus.

Bacterial Conjunctivitis

Bacteria that cause conjunctivitis can be transmitted by touching your eyes with unclean hands or sharing things like eye makeup, eyedrops, contact lens cases, or towels. It can be caused by bacteria including Staphylococcus aureus, Streptococcus pneumoniae, Moraxella catarrhalis, or Haemophilus influenza.

A serious type of conjunctivitis (ophthalmia neonatorum) can also be contracted by babies as they pass through the birth canal.

Allergic Conjunctivitis

Any allergy trigger can cause allergic conjunctivitis, including seasonal allergies, food allergies, or contact dermatitis of the eyelids (often caused by rubbing the eyes). 

One unique type, called giant papillary conjunctivitis (GPC), is triggered by the ongoing presence of a foreign body in the eye, such as contact lenses.

Chemical Conjunctivitis

Also known as toxic conjunctivitis, this can be caused by anything in the environment that irritates or injures the eye, such as smoke, fumes, acid exposure, or chlorine from a pool.

Inflammatory/Autoimmune

This can happen in conditions like ocular rosacea/dry eye, Sjogren's, and thyroid eye disease.

Symptoms

The symptoms of pink eye are triggered when the immune system responds to an infection or irritant with inflammation. Blood vessels dilate to help immune cells reach the area, causing redness and swelling.

If there is an infection, the accumulation of dead white blood cells and dead bacteria (or viruses) can lead to the formation of pus.

Conjunctivitis symptoms may include:

• Pink or red discoloration of one or both eyes
• Gritty feeling in the affected eye
• Discharge from the eye that can form a crust, especially at night
• Itchy or burning eyes 
• Excessive tearing
• Swollen eyelids
• Blurred vision
• Increased sensitivity to light

Symptoms can vary based on the type of conjunctivitis you have. When it’s caused by allergies, you may have itching and tearing without a thick discharge or crusting.

Bacterial conjunctivitis usually occurs with thick yellowish discharge that can cause your eyes to get crusty and stick together. Viral conjunctivitis typically has a watery, rather than a thick discharge. With chemical conjunctivitis, you may have watery eyes and mucus discharge, with symptoms varying in severity depending on the substance.

Diagnosis

If you have symptoms of pink eye, make an appointment to see your primary care physician or eye doctor.

Your healthcare provider will ask you about your symptoms and health history, including eye trauma or contact with others who have had pink eye.

They may examine your eye with a penlight or ophthalmoscope to illuminate or magnify the structures. Your practitioner may gently flip up your upper eyelid to see if there's a foreign body stuck under your eyelid. You may also be asked to read an eye chart to test your vision.

Usually your healthcare provider can tell if you have pink eye just by observation. If you are diagnosed with pink eye, the practitioner will want to determine whether the cause is infectious, allergic, or toxic. They will assess whether:

• One or both eyes are involved (as bacterial infections usually only affect one eye, while viral infections and allergies most commonly affect both eyes)
• There is visible discharge (indicative of infection)
• The discharge is thick or thin
• There is bleeding in the eye
• You have swollen lymph nodes
• You have allergy symptoms, such as hives or allergic rhinitis

Depending on the type and severity of your condition, your healthcare provider may want to get a sample of eye discharge to identify the cause of infection. Other tests may include a rapid adenovirus screening to confirm EKC or a fluorescein eye stain to look for abrasions or evidence of a sore or lesion (such as might occur with the herpes simplex virus).

In some cases, your primary care provider may determine that you need a referral to an ophthalmologist or an allergist. The American Academy of Ophthalmology recommends that patients be referred to an ophthalmologist when experiencing vision loss, moderate or severe pain, issues with the cornea, scarring of the conjunctiva, lack of response to treatment within a week, recurring conjunctivitis, or a history of herpes simplex virus eye disease.

Treatment

The treatment of pink eye is dependent on the underlying cause. In some cases, the symptoms may resolve on their own. In other cases, they may require treatment with topical eye drops or oral medications to treat an underlying infection.

Among the treatment approaches:

• Bacterial conjunctivitis: Uncomplicated cases can often be treated with antibiotic eye drops or topical ointments. In some cases, an oral antibiotic may be prescribed. Symptoms tend to resolve within three to four days. Most cases of ophthalmia neonatorum are avoided today due to the standard practice of applying a topical antibiotic into the eyes of newborns upon delivery.
• Viral conjunctivitis: As with many viral infections, like the common cold, the illness simply needs to run its course. This can take anywhere from two to three weeks. If there is severe pain or discomfort, steroid eye drops may be used to provide relief. Oral antivirals may be prescribed in certain cases.
• Allergic conjunctivitis: Removal of the allergy trigger is the best treatment. Antihistamines and/or topical steroid eye drops may also be prescribed.
• Chemical conjunctivitis: Treatment involves flushing the eyes with water or a saline wash. Serious cases may require topical steroids. Severe chemical injuries, particularly alkali burns, are considered medical emergencies and are treated in the same way as a burn injury.
• Inflammatory/autoimmune: Treatment of the underlying problem may reduce eye involvement.

Easing Symptoms

You can help ease symptoms for all types of conjunctivitis treatment with the following at-home steps:

• Use a warm compress. Soak a washcloth in warm water, wring out any extra water, and apply gently to closed eyelids. Use a different washcloth on each eye so you don’t spread the infection.
• Stop wearing contact lenses. To help your eyes heal, wear your glasses until your symptoms are gone and your eyes are back to normal. If contacts are the likely cause of conjunctivitis, your eye doctor may need to change your prescription to another type of lens.
• Use over-the-counter eye drops. For viral or bacterial conjunctivitis, lubricating eyedrops (artificial tears) can provide some relief. With allergic conjunctivitis, lubricating eyedrops can sometimes help flush out allergens. You can also try using a drop containing an antihistamine. Avoid red-reducing eyedrops, which can make some symptoms worse.
• Take over-the-counter pain medication. For discomfort or pain, try an oral nonsteroidal anti-inflammatory drug like ibuprofen.

Prevention

You can prevent getting infectious conjunctivitis by following these tips: 

• Wash hands regularly.
• Keep your hands away from your eyes.
• Avoid sharing personal items, like towels, facecloths, make-up brushes, and anything that comes into contact with the eye or eyelid.

If you have conjunctivitis caused by a bacteria or virus, you can keep from spreading it to others by practicing the same tips above, as well as the following:

• Wait until your symptoms are gone before returning to work or school. If you have a bacterial infection, ask your doctor if you can return after taking an antibiotic for 24 hours.
• Gently wipe discharge from your eyes using fresh cotton balls for each eye. Don’t use the same one for both eyes. Discard them in the trash when finished and wash your hands.
• Wash hands after applying ointment or eye drops.
• Wash or change pillowcases, sheets, and towels each day.

A Word From Verywell

Conjunctivitis is usually a minor eye infection, but it can develop into a more serious condition if left untreated. While many forms of pink eye can be treated by a general practitioner or pediatrician, severe cases (or those that fail to respond to therapy) should be seen by an ophthalmologist.