Ans. d. Reactivation of HSV-1 Fever blisters can occur due to reactivation of HSV-1. Oral vesicular lesions of mouth (fever blisters, cold sores) are more commonly associated with recurrent injection than the primary infection. "The most common site of cutaneous herpes infection is the face-on the cheeks, chin, around the mouth or on the forehead. Lesions may also appear on the buttocks in infants as 'napkin rash'. The typical lesion is the 'fever blister' or herpes febrilis, caused by viral reactivation in febrile patients." Herpes Simplex Virus HSV-1 causes cold sores; HSV-2 causes genital herpes. Primary Infection Inoculation of HSV-1 at mucosal surfaces or skin sites permits entry of the virus into epidermis, the dermis and eventually to sensory and autonomic nerve endingsQ Sudden onset with the appearance of multiple characteristic vesicular lesions superimposed uponan inflammatory erythematous base. Associated with systemic symptoms such as fever and malaiseQ Cold sores with symptoms: Painful blisters on the mouth, nose or throatQ Mouth and throat painQ LymphadenopathyQ Fever and body acheQ Gingivostomatitis and pharyngitis are the most frequent clinical manifestation of first episode of HSV-1 infectionQ Recurrent Infection Once HSV infection has occurred, the virus lies in a latent state in nerve cell bodies in ganglion and can reactivate. Severity and number of lesions is considerably less with reactivation Rarely associated with systemic signs or symptoms Oral vesicular lesions of the mouth (fever blisters, cold sores) are more commonly associated with recurrent infection than the primary infections. Herpes labialis (cold sore) is the most frequent sign of reactivation diseasedeg Involvement of the oral cavity and lips are common, most patients develop prodromal symptoms about 24 hours before the appearance of painful lesions at the lip borders.