Orofacial herpes (cold sores or fever blisters) is most commonly caused by herpes simplex virus type 1 (HSV-1) but may be caused by herpes simplex virus type 2 (HSV-2) as well. The condition is highly contagious and is spread by direct contact or through contact with the secretions of asymptomatic individuals who shed the virus. Childhood infection is common via child-to-child contact or kissing by a parent.

Primary herpetic gingivostomatitis is an acute infection of the oral mucous membranes by HSV that results from initial exposure to the virus. Most primary exposures (approximately 90%) are subclinical and asymptomatic. Herpetic gingivostomatitis occurs most often in children between ages 10 months and 5 years, but it can occur at any age. Patients experience a flu-like illness with fever, loss of appetite, malaise, and lymphadenopathy. Painful mouth sores and a sore throat develop, and difficulty eating and swallowing places the patients at risk for dehydration. The systemic and oral signs and symptoms develop within days of each other.

The virus establishes lifelong latency, and both asymptomatic reactivation as well as recrudescence are common. In recrudescence, patients may report a prodrome of burning, itching, and a tingling sensation before the actual lesions appear. HSV recrudescence on the lips is also known as cold sores, fever blisters, or herpes labialis; inside the mouth, lesions only occur on the keratinized tissues of the tongue dorsum, hard palatal mucosa, and gingiva in healthy hosts, but they may occur on any surface in the immunocompromised host. Intraoral involvement in recrudescent disease in immunocompetent hosts is rare.

Infection with HSV can present in a variety of ways. In some cases, it is preceded by a prodrome, which may consist of pain, tenderness, or burning; in others, infection is asymptomatic. After the primary infection, the virus remains dormant and may be reactivated by various stimuli, including illness, stress, immunosuppression, or ultraviolet (UV) light.

HSV can also disseminate, occurring on skin areas distant from the lips. Two general groups of patients are at risk to develop disseminated HSV: patients with underlying skin disease and immunocompromised patients.

Neonatal HSV is covered separately.

Localized HSV in areas other than the face and mouth, such as herpetic whitlow, are discussed separately. Other related topics include HSV blepharitis, HSV conjunctivitis, HSV encephalitis, HSV gladiatorum, HSV keratitis, and HSV pneumonia.