Where is the most common intraoral location of RECURRENT herpes simplex virus (HSV-1) infection?

Herpes simplex virus type 1 (HSV-1) causes two forms of oral infection: PRIMARY herpetic gingivostomatitis — the initial infection affecting children/young adults, with widespread vesicles/ulcers on both keratinized and non-keratinized mucosa, fever, and lymphadenopathy. RECURRENT herpes labialis (cold sore / fever blister) — the most common form of recurrent HSV-1; lesions appear at the MUCOCUTANEOUS JUNCTION of the lip (vermillion border), where labial mucosa meets perioral skin; preceded by prodromal burning/tingling; clusters of vesicles that rupture and crust. The virus remains latent in the trigeminal ganglion and reactivates with stress, UV exposure, fever, or immunosuppression. Note: Intraoral recurrent HSV appears on KERATINIZED ATTACHED mucosa (hard palate, attached gingiva) — NOT movable mucosa. Herpes labialis at the mucocutaneous junction is the most common presentation overall and is high-yield for the INBDE.