Herpes simplex lesions are caused by the herpes simplex virus and are characterized by small, fluid-filled blisters that appear on the skin or mucous membranes. Synonyms for herpes simplex lesions include cold sores, fever blisters, oral herpes, and genital herpes. Cold sores typically appear on or around the mouth, while genital herpes causes blisters on or around the genitals. Oral herpes is usually transmitted through close contact with an infected person, while genital herpes spreads through sexual contact. While there is no cure for herpes simplex, antiviral medications can help alleviate symptoms and prevent future outbreaks.