Picture of Herpes Simplex Virus Type 1
Human herpesvirus 1 (HHV-1), also known as herpes simplex type 1 (HSV-1), is the virus that typically causes cold sores, also known as fever blisters. Factors such as stress, sun exposure, surgery, illness, and fever can cause the virus to reactivate and lead to an outbreak of new sores. Cold sores and fever blisters may occur inside the mouth, on the lips, or on the area around the mouth. Although they are annoying and the sores can be painful, oral herpes outbreaks are not dangerous in healthy people. People who have compromised immune systems may suffer more serious complications from oral herpes outbreaks and should seek medical treatment.
Text Reference: "Herpes Simplex: Who Gets and Causes." American Academy of Dermatology.