Phlyctenular keratoconjunctivitis (PK) is an inflammatory eye condition resulting from an immune overreaction to pathogens, such as bacteria, fungi, and parasites. The condition causes inflammation of the cornea and conjunctiva.

The cornea is the thin membrane that covers the iris and pupil, and the conjunctiva is the membrane that lines the eyelids and the whites of the eyes.

In this article, we describe what PK is, including its causes and symptoms. We also provide information on how doctors diagnose and treat PK.

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PK is an immune hypersensitivity reaction to a pathogen, such as a bacterium, fungus, or parasite. This reaction causes inflammatory nodules to develop on the cornea or conjunctiva of the eye.

Although PK can affect people of all ages, it is more common in children aged 6 months to 16 years. Females are also more likely than males to develop PK.

PK is not an infection. Rather, it is an immune reaction that exposure to certain infectious pathogens can trigger.

Some organisms that may cause PK include:

  • bacteria, such as:
    • Staphylococcus aureus
    • Mycobacterium tuberculosis
    • Chlamydia
  • parasites, such as:
    • Ascaris lumbricoides
    • Ancylostoma duodenale
  • fungi, such as:

In the United States, the most common cause of PK is S. aureus. This bacterium lives naturally on and inside the human body, including on the surface of the eyes and eyelids.

Researchers believe that people may develop PK after re-exposure to an organism with which they had contact in the past. Reinfection causes an immune system overreaction, which triggers an allergic reaction in the conjunctiva or cornea.

Experts do not yet understand why PK is more common among children than among adults.

PK symptoms range from mild to severe. For instance, inflammatory nodules on the conjunctiva may cause only mild irritation, whereas inflammatory nodules on the cornea may cause significant pain and other symptoms.

The typical symptoms of PK include:

Some people with PK also develop blepharitis, which is inflammation of the eyelids. The symptoms of blepharitis include:

  • swelling
  • discoloration
  • crusty skin on the edges of the eyelids

The nodules associated with PK may persist for anywhere from a few days to a couple of weeks. In severe cases, corneal ulcerations may develop. This can lead to complications, such as corneal scarring and vision loss.

A doctor will conduct a thorough physical examination of the eyes to diagnose PK. If a person also has blepharitis, the doctor may perform a culture of the eyelids to determine the pathogen responsible.

The treatment for PK typically includes a combination of anti-inflammatory medications and antibacterial eye drops, along with appropriate eyelid hygiene.


The main treatment for PK is topical corticosteroids. This medication decreases inflammation and swelling.

People using topical corticosteroids should talk with their doctor about how to taper the dose to avoid a reoccurrence of PK.

Topical antibiotics

Topical antibiotic eye drops help treat bacterial infections associated with PK. This treatment typically lasts a few weeks.

Immune suppressants

Immune suppressants are medications that inhibit the immune system. They may help prevent flare-ups of PK.

A small 2018 study investigated the effectiveness of tacrolimus, an immune suppressant, in five participants with severe, recurrent PK. The participants received tacrolimus alongside topical steroids during the active phase of their condition and then continued treatment with topical tacrolimus after remission. The results indicated that tacrolimus was effective in maintaining long-term remission in people with recurrent PK.

Light sensitivity strategies

Some people with PK develop an oversensitivity to light that may cause significant discomfort. Strategies to reduce discomfort include:

  • keeping indoor lights and screens dim
  • staying out of direct sunlight, where possible
  • wearing tinted glasses

Eyelid hygiene management

The management of PK also includes practicing appropriate eyelid hygiene to treat blepharitis and reduce symptoms. People can try the following:

  • Applying warm compresses to the eyelids: Placing a warm, damp washcloth over the eyelids can help remove eye crust and ease irritation. People can try applying warm compresses several times a day.
  • Cleansing the eyelids: Cleansing the eyelid at the base of the eyelashes helps treat underlying infections. People should do this once or twice a day to help prevent symptoms from returning. A person can follow the steps below:
    • Step 1: Mix a solution consisting of half a cup of warm water and three drops of baby shampoo.
    • Step 2: Dip a cotton swab into the solution and use the swab to cleanse the eyelid gently.
    • Step 3: Rinse the eyelids gently and thoroughly.

Phlyctenular keratoconjunctivitis is a condition involving inflammation of the cornea and conjunctiva of the eye. The condition occurs as a result of an immune system overreaction to a pathogen, such as a bacterium, fungus, or parasite.

PK may cause inflammatory nodules to develop on the cornea and conjunctiva. The symptoms may include eye pain, excessive tearing, and sensitivity to light. A doctor can diagnose PK by conducting a thorough eye examination, which may include a culture of the eyelid to test for pathogens.

The treatment for PK typically includes a combination of topical corticosteroids, antibiotic eye drops, and appropriate eyelid hygiene.