Eye infection

Acute cataracts (infectious conjunctivitis)
Most often it occurs in children. Acute cataracts are an inflammation of the outer retina, the conjunctiva. Inflammation is caused by viruses or bacteria. Usually starts in one eye, but often spreads to the other eye. It feels as if something has entered the eye. There may be slight burning, but not pain. Typically, the eyes are often re-glued after sleep.

Allergic cataracts (allergic conjunctivitis)
Typically occurs in children and with hay fever, usually in spring and summer. Causes itching, red eyes, tearing often with mucus threads, photosensitivity, possibly allergic symptoms from other organs (nose, lungs, skin). Both eyes are usually irritated.

Rupture or ulceration of the cornea (corneal erosion)
Rupture or scratching of the cornea after external damage or damage from contact lenses. Causes pain, photophobia, foreign body sensation, tearing, red eye.

Foreign body on the eye
Very common and usually known damage mechanism, for example during welding. Causes pain, photophobia, foreign body sensation, tearing, red eye.

Snow blindness, sun blindness
Due to the fact that you have been exposed to strong ultraviolet light. It usually takes 4-12 hours before the eye problems occur. Gives pain, photophobia and foreign body sensation on the eye. The condition resolves on its own within 24-48 hours

Inflammation of the iris (iridocyclitis) or cornea (keratitis)
Most often unilateral, painful, red eye, photophobia, tearing, possibly. blurred vision. Requires treatment by an ophthalmologist immediately.

The most common causes of red eye are infectious cataracts and allergic reaction (hay fever). These are innocent conditions that can go away on their own, but persistent symptoms indicate that you should consult a doctor. Snow blindness / sun blindness also does not require medical treatment. All other forms of red eye require immediate medical attention.