Condition
Herpes simplex keratitis (cold sore in the eye)
Clinically reviewed · Last reviewed 2026-06-13
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.
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.