Differential Diagnosis for Eyes Constantly Watering

• Single most likely diagnosis
  • Allergies: This is often the most common cause of constantly watering eyes, as allergic reactions can lead to the release of histamine, which in turn causes blood vessels in the eyes to swell, leading to increased tear production.
• Other Likely diagnoses
  • Dry eye syndrome: Although it seems counterintuitive, dry eyes can sometimes cause the eyes to water constantly. This is because the lack of moisture in the eyes can lead to irritation, which the body tries to compensate for by producing more tears.
  • Blepharitis: This is an inflammation of the eyelids that can cause irritation and lead to excessive tearing.
  • Conjunctivitis (pink eye): This is an infection or inflammation of the outer membrane of the eyeball and the inner eyelid, which can cause the eyes to water constantly.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Glaucoma: While not typically associated with watering eyes as a primary symptom, certain types of glaucoma can cause eye pain and blurred vision, and in rare cases, may lead to increased tearing.
  • Orbital cellulitis: This is a serious infection of the tissues surrounding the eye, which can cause pain, swelling, and increased tearing, among other symptoms.
  • Corneal ulcer: A serious infection of the cornea that can cause severe pain, blurred vision, and increased tearing.
• Rare diagnoses
  • Thyroid disorders: Certain thyroid conditions, such as Graves' disease, can cause the eyes to bulge (exophthalmos) and lead to increased tearing due to the swelling of tissues behind the eye.
  • Sjögren's syndrome: An autoimmune disorder that can cause dryness in the eyes and mouth, but in some cases, can also lead to increased tearing due to the body's attempt to compensate for the dryness.
  • Lacrimal duct obstruction: A blockage in the tear ducts that can cause tears to accumulate in the eye and overflow, leading to constantly watering eyes.