Differential Diagnosis for an Itchy Eye

• Single most likely diagnosis:
  • Allergic conjunctivitis: This is the most common cause of an itchy eye, often associated with other symptoms like redness, tearing, and stringy discharge, especially in individuals with a history of allergies.
• Other Likely diagnoses:
  • Dry eye syndrome: This condition can cause itchiness, along with feelings of grittiness or burning in the eyes, often due to inadequate tear production or poor tear quality.
  • Blepharitis: Inflammation of the eyelids can lead to itchy, red, and swollen eyelids, sometimes accompanied by a gritty sensation in the eyes.
  • Conjunctivitis (viral or bacterial): While not always itchy, some forms of conjunctivitis can cause itchiness along with redness, discharge, and a sensation of having something in the eye.
• Do Not Miss diagnoses:
  • Acute angle-closure glaucoma: Although rare, this condition is an emergency and can present with severe eye pain, blurred vision, headache, nausea, and vomiting, along with eye itchiness in some cases.
  • Herpes zoster ophthalmicus: Shingles affecting the eye can cause severe pain, redness, and potentially lead to serious complications if not promptly treated.
• Rare diagnoses:
  • Phlyctenular keratoconjunctivitis: An allergic type of conjunctivitis that can cause itchy, small nodules on the conjunctiva or cornea, often associated with rosacea or eczema.
  • Vernal keratoconjunctivitis: A seasonal allergic condition that affects the eyes, causing intense itching, stringy discharge, and sometimes small, hard bumps under the eyelids.