Cold sores, also known as fever blisters, are caused by the herpes simplex virus (HSV). They are small, painful, fluid-filled blisters that typically appear around the mouth or on the lips. Cold sores are contagious and can be spread from person to person through direct contact or through contact with contaminated surfaces.
The length of time that cold sores are contagious can vary depending on the individual and the stage of the infection. Generally, cold sores are contagious for the entire duration of the outbreak, from the first tingling sensation until the blisters and scabs have completely healed. This can take anywhere from a few days to a couple of weeks.
Cold sores are most contagious when the blisters are present and oozing. During this stage, the virus can easily be spread through contact with the blisters or body fluids. Even after the blisters have dried and scabbed over, the virus can still be spread through direct contact with the scab or by touching the area with unwashed hands.
It's important to practice good hygiene to reduce the risk of spreading the virus. This includes washing your hands regularly, avoiding sharing personal items such as towels or lip balm, and not kissing or touching someone else's cold sores. If you do come into contact with someone else's cold sores, it's important to clean the affected area and your hands immediately afterwards.