Research has shown that sun exposure in people infected with oral herpes (HSV-1), may cause a flare up, or outbreak of fever blisters and cold sores.
According to MSN.com, “Flare-ups can … occur when someone is under emotional stress, ill with fever or menstruating.” (1)
Sometimes an injury can cause an outbreak, and sometimes flare-ups happen without explanation.
An outbreak, after exposure to the sun, is common however. “Exposure to UV radiation is recognized to suppress cell-mediated immunity and therefore could adversely affect the course of a viral infection…These are herpes simplex, in which sunlight exposure can cause reactivation….” (Photochemistry and Photobiology, 2006) (2)
It is normal for herpes outbreaks to occur after exposure to sunlight.
Sunburn can cause cell damage in the lips. For example, a person may become sunburned during outdoor activity in the summer and then go on to develop oral herpes symptoms.
Some people believe that using a sunscreen can help prevent an oral herpes outbreak. However, “In a study of 51 patients, which was performed under natural conditions, use of a sunscreen lotion with a high protective factor did not result in a lower incidence of herpes labialis.” (Canadian Family Physician, December 2008) (3)
People develop herpes outbreaks during the summer. And, sunscreen doesn’t help.
“The first symptom of an outbreak is an unpleasant tingling feeling in the skin. After a short while, a number of fluid-filled blisters appear. The sores become covered by scabs that, typically, fall off after 8 to 10 days. The virus can spread until the sores are completely covered by scabs. Around 20 per cent of the people with HSV antibodies have recurrent attacks of cold sores throughout their lives.” (Netdoctor.co.il) (4)
In the other 80%, herpes establishes what scientists call a latent infection.
When a virus is latent, it acts as if it is asleep or dormant. The moment the immune system is weakened, however, the herpes virus can “wake up” and become active again.
The best defense against a latent herpes infection is a healthy immune system.