---
title: "Herpes simplex keratitis (cold sore in the eye)"
description: "What herpes simplex keratitis is, why the cold-sore virus can infect the cornea, warning symptoms, and why prompt antiviral treatment protects sight."
url: https://eyehealthguide.org/conditions/herpes-simplex-keratitis/
source: Eye Health Guide
licence: "General information only. Cite the URL and the named medical reviewer."
---

Condition

# Herpes simplex keratitis (cold sore in the eye)

Medical reviewer [Mr Mohamed Mohyudin](https://eyehealthguide.org/reviewers/mohamed-mohyudin/)· Last recorded site review July 6, 2026

### About this review

This page inherits the site’s previous review record. A separate, current article sign-off has not yet been recorded.

[How review works](https://eyehealthguide.org/reviewers/) · [Official biography & credentials](https://mohamedmohyudin.co.uk/author/mohamed-mohyudin/)

Quick answer

Herpes simplex keratitis is an infection of the cornea by the cold-sore virus (HSV-1). It causes a painful, red, watering eye with blurred vision and light sensitivity. It needs prompt antiviral treatment to prevent scarring and protect sight, and can recur over time.

### On this page ⌄

1. Your next step
2. What it is
3. Common symptoms
4. Causes and recurrence
5. Treatment
6. Related conditions
7. Frequently asked questions

## What it is

The same herpes virus that causes cold sores on the lip can infect the cornea, the clear front of the eye. This is one of the most common causes of corneal infection and can leave scars that affect vision if not treated promptly.

## Common symptoms

Symptoms usually affect one eye and may follow a cold sore or stress.

- Painful red eye with watering
- Blurred vision and light sensitivity
- A feeling of something in the eye
- Sometimes a branching ulcer visible on the cornea

## Causes and recurrence

After a first infection, the virus can remain in the body and reactivate during stress, illness, sunlight or lowered immunity. Repeat episodes can cause cumulative scarring, so long-term preventive treatment is sometimes used.

## Treatment

Antiviral eye drops or tablets are the main treatment and should be started promptly. Steroid drops are only used under close supervision once infection is controlled, as they can worsen herpes if used incorrectly.

## Related conditions

## Frequently asked questions

### Can a cold sore spread to the eye?

Yes. The cold-sore virus (HSV-1) can infect the cornea, causing a painful red eye with blurred vision. Wash hands after touching a cold sore and seek prompt care if the eye becomes red and painful.

### Is herpes eye infection contagious?

It is not spread like conjunctivitis, but the virus can be present in tears during active infection. Good hygiene and avoiding sharing towels help reduce spread.

### Can herpes keratitis cause permanent vision loss?

Treated early, most episodes heal well. Delay or repeated scarring can permanently affect vision, which is why prompt antiviral treatment matters.

Your next step

## Take this to your appointment

Write down what has changed, when it started, your current medicines and the questions you want answered. Take these to your eye-care appointment.

Sudden loss of sight, severe eye pain or a dark curtain across vision needs immediate assessment. Do not wait to complete a worksheet.

## Sources for this information

These references support the information on this page. Follow the linked source for its full context.

- [NHS - Herpes simplex eye infections](https://www.nhs.uk/conditions/herpes-simplex-eye-infections/)