What can cause it?
Redness and pain are the eye's general response to irritation, infection or inflammation, so the list of possible causes is wide:
- Dry eye disease
- Blepharitis
- Allergies and allergic conjunctivitis
- Conjunctivitis
- Corneal irritation or infection
- A foreign body or a scratch on the eye surface
- Uveitis, or inflammation inside the eye
- Contact lens–related problems
- Acute glaucoma