
Fatigue

Viral infection or fever

Hormonal changes (e.g. menstruation)

Stress

Sunlight and wind

Changes in the immune system
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).