Fever blisters, also known as cold sores or labial herpes, are small, painful, and itchy lesions that form on the face or inside the mouth. These blisters typically appear on areas such as the lips, chin, cheeks, or inside the nostrils, though they can occasionally develop on the gums or the roof of the mouth. They are caused by the herpes simplex virus type 1, which remains dormant in the body and can be reactivated by stress, sunburn, or infections like colds. After the age of 35, these outbreaks tend to become less frequent. Applying sunscreen with an SPF of 15 or higher to the lips can help prevent recurrences triggered by sun exposure.The herpes simplex virus is highly contagious when fever blisters are visible and can be transmitted through kissing. Children often contract the virus by coming into contact with someone who has an active sore and may spread it further by touching the blister and then other children. Individuals with fever blisters should avoid touching the sores to prevent spreading the virus to other body parts, such as the eyes or genitals.While there is no cure for fever blisters, certain treatments can alleviate pain and discomfort. These include ointments that numb the affected area, antibiotics for secondary bacterial infections, and creams that soften the crusts of the sores. Antiviral medications can prevent the virus from replicating and, when taken in pill form, may reduce the severity and frequency of outbreaks.Fever blisters have been a common affliction for thousands of years. In ancient Rome, an outbreak led Emperor Tiberius to prohibit kissing during public ceremonies. Today, fever blisters continue to affect large numbers of people, with approximately 100 million cases occurring annually in the United States alone. Fever blisters are sometimes referred to as herpes febrilis in Latin.