Why does allergic conjunctivitis cause red eye?

The conjunctiva is the thin lining over the white of the eye and inside the eyelids. When it encounters a trigger such as pollen, animal dander, dust mites, or mould, immune cells can release histamine. This leads to increased blood flow, watering, itchiness, and swelling, so the eye may look bloodshot.

Red Eye is a very common presentation of Allergic Conjunctivitis. Allergy-related redness often occurs with itchiness and watery eyes, but a red eye can also result from infection, dryness, an eyelid problem, a contact lens issue, or an injury.

Avoid rubbing the eye, since friction can worsen inflammation. Use a cool clean compress over the closed eyelid and wash hands before touching the face. If an outdoor trigger seems relevant, rinse your face after returning indoors and keep pollen away from bedroom fabrics where possible.

A pharmacist or clinician can help you choose suitable lubricating or allergy eye drops. Mention contact lenses before using drops, and follow advice about when lenses should be left out while the eye is irritated.

Get prompt medical care for eye pain, sensitivity to light, reduced or blurred vision, a severe headache with eye redness, major swelling, or a recent injury. Seek urgent help after a chemical splash and rinse the eye continuously with clean running water while arranging care. Book an assessment if redness persists, keeps returning, or is accompanied by thick discharge.

Ask whether the pattern looks allergic, which triggers may be relevant, and whether drops or nasal allergy treatment could help. Tell the clinician about one-sided symptoms, contact-lens wear, discharge, vision changes, and any treatment you have already tried.