The short answer is yes, stress can cause cold sores! Stress can cause recurrency of cold sores, if you have previously been exposed to the virus. We know that the main cause of cold sores is the contagious herpes virus, but some people are more prone to cold sores than others. If you’re experiencing stress and anxiety, your immune system is likely weaker than usual, which leaves you more susceptible to viral infections, including cold sores.