Thanks for your query. Cold sores are caused by herpes
virus. It has been documented that stress can result in activation of the virus. However, citalopram
has not been documented to have the mentioned side effect of cold sores.Stress reduction techniques like breathing relaxation, yoga and meditation
practices can be useful. However, an additional medical evaluation with a general medicine practitioner is recommended to rule out other medical causes.
Dr Sundar Gnanavel