Cold sores are small, painful blisters that appear on or around the lips, caused by the herpes simplex virus (HSV-1). Once contracted, this virus remains in the body for life, potentially reactivating to cause outbreaks. A common concern during an outbreak is understanding its contagiousness, especially when the sore begins to scab over.
Contagiousness During Scabbing
When a cold sore scabs over, it indicates the healing process is underway, and the risk of transmitting the virus significantly decreases. While scabbing suggests a reduction in viral shedding, it is still technically possible to spread the virus. The scab can crack, especially with facial movements like eating or smiling, potentially exposing underlying fluid that contains the virus. Therefore, even in the scabbing phase, precautions remain necessary until the skin fully returns to its normal appearance.
The Full Contagious Period of a Cold Sore
A cold sore’s contagiousness begins before any visible blisters appear, starting with the initial tingling, itching, or burning sensation known as the prodromal stage. Within 24 to 48 hours, small, fluid-filled blisters form. These blisters then rupture, oozing a clear or yellowish fluid during the “weeping phase.”
This blistering and weeping stage represents the period of highest risk for transmission, as the fluid contains a high concentration of the virus. Following the weeping stage, the blisters dry out and form a crust or scab. While the risk of transmission lessens during this crusting phase, the cold sore remains contagious until the scab falls off and the skin has healed, which can take up to two weeks from the initial symptoms.
Preventing Transmission
To prevent the spread of cold sores, especially when they are most contagious, several measures can be taken. Avoid direct skin-to-skin contact, such as kissing, until the sore has completely healed. Sharing personal items like eating utensils, drinking glasses, towels, lip balm, or other cosmetics that may have come into contact with the sore should also be avoided.
Frequent hand washing with soap and water is recommended, especially after touching the cold sore. Avoid touching the cold sore unless applying medication, to prevent spreading the virus to other parts of your body or to others. Be mindful around infants and individuals with weakened immune systems, as they are more susceptible to infection.