Cold Sores and Kissing: How Contagious Are They Really?

Yes, kissing can transmit herpes simplex virus (HSV-1), the cause of cold sores.

Transmission Facts

• Direct contact with active lesions (vesicles, ulcers) or infected saliva.
• Asymptomatic shedding: Virus present on skin/saliva without visible sores (10–20% of days).
• Highest risk: During prodrome (tingling) through crusting stage.
• Autoinoculation: Touching sore → touching eyes/genitals can spread virus to other sites.

Risk Factors for Acquisition

• Partner with active outbreak
• Immunosuppression (stress, illness, medications)
• Breaks in oral mucosa

Prevention

• Avoid kissing/contact with lesions.
• Don't share utensils, drinks, lip products, towels during outbreak.
• Wash hands after touching sore.
• Antiviral suppressive therapy (valacyclovir, acyclovir) reduces shedding/transmission by ~50%.
• Condoms/dental dams for oral-genital contact.

Key Points

• HSV-1 is extremely common (~67% global prevalence <50 years old).
• Most infections acquired in childhood non-sexually.
• Once infected, virus remains latent in trigeminal ganglion for life.
• Recurrences triggered by stress, UV, illness, hormonal changes.

If you have frequent/severe outbreaks, consult a clinician for suppressive therapy.