The herpes viruses cause cold sores, which most commonly appear on the lips or genitals. They affect around seven in 10 people in the UK.
Cold sores on the lips most commonly get passed on by being kissed by someone with an active cold sore.
They begin as a small red patch that blisters before bursting, leaving a raw area that scabs.
Cold sores are only transmitted by direct skin contact, not by sharing items such as towels or cutlery.
Once injected, sufferers may experience a fever and flu-like symptoms.
After healing, cold sores can reappear if triggered by stress, illness, alcohol or too much sunlight.
Antiviral medication may be prescribed if someone frequently suffer outbreaks.
Source: Herpes Viruses Association