Although complications from cold sores are rare, they can include:
- Eye infections: The herpes simplex virus (HSV-1) can spread to the eye when someone touches a cold sore and then touches their eye. If HSV-1 spreads to the eye, it can cause HSV keratitis — a potentially serious infection of the cornea. Severe HSV keratitis infections can lead to blindness.
- Genital sores: HSV-1 can spread to the genitals through oral sex, producing warts or ulcers on the genitals or anus. But even though people sometimes call it oral herpes, HSV-1 is not the same as HSV-2, the sexually transmitted virus that causes most cases of genital herpes.
For certain groups of people, cold sores can lead to serious complications. The following groups of people should receive medical treatment immediately if they have a cold sore:
- Newborns: Babies under 6 months old may develop complications such as high fever and seizures because their immune systems aren’t fully developed.
- Immunocompromised people: For people with weakened immune systems, the herpes simplex virus can lead to encephalitis (swelling of the brain). If you have HIV or are undergoing chemotherapy, cold sores could be more severe and could take longer to go away.
- People who have eczema: The herpes simplex virus can cause a life-threatening infection called eczema herpeticum in adults and children with eczema. It is important to see your doctor right away if you have eczema and you develop a cold sore.