Viral infection or fever
Hormonal changes (e.g. menstruation)
Sunlight and wind
Changes in the immune system
There is no cure for cold sores,2 but there are simple things you can do reduce the risk of spreading them to other parts of your body and to other people. LEARN MORE
2. Mayo Clinic. Cold sore. 2015. Available at: https://www.mayoclinic.org/diseases-conditions/cold-sore/basics/causes/con-20021310?p=1 (accessed 14/11/17).