---
title: What causes conjunctival injection?
description: "Conjunctival injection is dilation of the superficial blood vessels in the conjunctiva, giving a bright red appearance. It usually indicates surface irritation or inflammation. ## Causes Infective or allergic conjunctivitis, dry eye, blepharitis, and minor trauma commonly produce conjunctival injection.…"
url: "https://bluefinvision.com/knowledge-base/topics/symptoms-signs/what-causes-conjunctival-injection/"
updated: "2025-12-12"
category: "Symptoms & Signs"
---

# What causes conjunctival injection?

Conjunctival injection is dilation of the superficial blood vessels in the conjunctiva, giving a bright red appearance. It usually indicates surface irritation or inflammation.

## Causes

Infective or allergic conjunctivitis, dry eye, blepharitis, and minor trauma commonly produce conjunctival injection. Less often, foreign bodies, chemical exposure, or contact lens complications are responsible.

- Redness is often more intense in the fornices and away from the cornea
- Discharge, itching, or grittiness frequently accompany injection
- Systemic infections and viral illnesses may include injected eyes
- Chronic injection can result from long-term drop use or ocular surface disease

## Clinical Significance

While many causes are benign, distinguishing simple conjunctivitis from early keratitis or uveitis is important. Examination looks for corneal staining, anterior chamber cells, and focal tenderness.

- Mild cases may be managed with lubricants and, when appropriate, topical therapy
- Contact lens wear should stop until serious causes are excluded
- Photophobia or vision loss with injection requires urgent assessment
- Public health advice may be needed for contagious conjunctivitis