An acute infectious disease, characterised by the development of groups of superficial vesicles, or blebs, in the skin and MUCOUS MEMBRANE. It is due to either Herpes simplex type 1 or 2 virus, and infection can occur at any time from birth onwards; however the usual time for primary infection with type 1 is between the second and 15th year. Once an individual is infected, the virus persists in the body for the rest of their life. It is one of the causes of scrum-pox. Type 2 causes HERPES GENITALIS.
Symptoms vary with the age of infection. In young infants, herpes simplex may cause a generalised infection which is sometimes fatal. In young children the infection is usually in the mouth, and this may be associated with enlargement of the glands in the neck, inability to feed, general irritability and fever. The condition usually settles in 7–10 days. In adults the vesicles may occur anywhere in the skin or mucous membranes: the more common sites are the lips, mouth and face, where they are known as cold sores. The vesicles may also appear on the genitalia (HERPES GENITALIS) or in the conjunctiva or cornea of the EYE, and the brain may be infected, causing ENCEPHALITIS or MENINGITIS. The first sign is the appearance of small painful swellings; these quickly develop into vesicles which contain clear fluid and are surrounded by a reddened area of skin. Some people are particularly liable to recurrent attacks, and these often tend to be associated with some debilitating condition or infection, such as pneumonia.
Except in the case of herpes of the cornea, the eruption clears completely unless it becomes contaminated with some other organism. In the case of the cornea, there may be residual scarring, which may impair vision.
Aciclovir is effective both topically as cream or eye drops or orally. In severe systemic infections it can be given intravenously.