What triggers cold sores?

Most of the time the outbreaks seem to have a life of their own and there is no one factor that appears to have initiated or caused the outbreak. There are a number of factors that are known to cause an outbreak of herpes labialis including:

1. Emotional and physical stress may alter or lower the immune system allowing the virus to awaken or reactivate.
2. Colds or other upper respiratory tract infection may also reactivate the virus. These cold sores are often called fever blisters.
3. Sun (including tanning beds)or wind exposure without protection, especially on the lips, may reduce the immune activity in the skin leading to a recurrence of cold sores.
4. Hormone changes such as those seen during menstruation
5. Local trauma or injury to the skin around the lips including dry cracked lips and injury to the skin following cosmetic surgery, chemical peels or laser therapy