• Allergies — Injury, such as from a blunt trauma or burn.
• Blepharitis — which is eyelid inflammation.
• Chalazion — caused by clogged oil glands on the eyelid.
• Complication from a recent eye surgery.
• Contact lens complication.
• Corneal abrasion (scratch): First aid
• Corneal herpes infection.
• Corneal ulcer.
• Dry eyes
• Ectropion — which is an outwardly turned eyelid.
• Entropion — which is an inwardly turned eyelid.
• Episcleritis — which is inflammation of the covering of the white part of the eye.
• Eye drops side effect or complication.
• Floppy eyelid syndrome — which happens when the eyelid can easily fold on itself.
• Foreign object in the eye: First aid
• Glaucoma — which is part of a group of conditions that damage the optic nerve.
• Hay fever
• Injury — such as from blunt trauma or a burn.
• Iritis — which is inflammation of the colored part of the eye.
• Keratitis — which is inflammation of the cornea.
• Orbital cellulitis — which is an infection of the area around the eye.
• Pink eye (conjunctivitis)
• Scleritis — which is inflammation of the white part of the eye.
• Subconjunctival hemorrhage (broken blood vessel in eye)
• Uveitis — a form of eye inflammation that affects the middle layer of tissue in the eye wall.

Seek immediate medical care if:

• Your eyesight changes suddenly.
• Red eye happens with a bad headache, eye pain, fever or if light starts to hurt your eyes.
• You also have an upset stomach or are throwing up.
• Red eye is caused by an object or chemical splashed in your eye.
• You suddenly begin to see circles around lights.
• You feel as if something is in your eye.
• You have swelling in or around your eye.
• You cannot open or keep your eye open.

When to make an appointment with a healthcare professional

Sometimes, having red eye for a short time is not a reason to worry. If you think the redness is caused by over-the-counter eye drops, try a different brand or take a break from using them.

Call a healthcare professional for an appointment if you have red eye that doesn't clear up after several days, especially if you have thick pus or mucous for week or more.

Contact your eye care professional if:

• You're having eye redness with pain.
• You've had eye surgery or an eye injection in the past.