Cold sore recurrences are very common. The virus stays in the ganglia in an inactive, or latent, form. During this time the virus does not replicate. It stays in this latent form for varying amounts of time. Certain triggers may cause the virus to travel down the nerve to the skin and cause symptoms to reappear. This is known as a recurrence.
Even with a normal immune system, recurrences can happen. Sometimes the recurrence occurs spontaneously. However, the following are known triggers that can stimulate a recurrence: physical stress, persistent stressors, anxiety, fever, exposure to ultraviolet light, sun exposure, nerve damage, tissue damage, a suppressed immune system, heat, cold, menstruation, other infections, fatigue or hormonal changes.