Cold sores, so called fever blisters, are groups of small blisters on the lip and around the mouth. The skin around the blisters is often red, swollen, and sore. The blisters may break open, leak a clear fluid, and then scab over after a few days. It is usually get healed after several days to 2 weeks.

What causes cold sores?

Cold sores, which are small and somewhat painful blisters that usually show up on or around a person's lips, are caused by the herpes simplex virus-1 (HSV-1). But they don't just show up on the lips. They can sometimes be inside the mouth, on the face, or even inside or on the nose. These places are the most common, but sores can appear anywhere on the body, including the genital area.

Genital herpes isn't typically caused by HSV-1; it's caused by another type of the herpes simplex virus called herpes simplex virus-2 (HSV-2) and is spread by sexual contact. But even though HSV-1 typically causes sores around the mouth and HSV-2 causes genital sores, these viruses can cause sores in either place.

How Do Cold Sores Spread?

Cold sores are really contagious. If you have a cold sore, it's very easy to infect another person with HSV-1. The virus spreads through direct contact — through skin contact or contact with oral or genital secretions (like through kissing). Although the virus is most contagious when a sore is present, it can still be passed on even if you can't see a sore. HSV-1 can also be spread by sharing a cup, eating utensils, or lip balm or lipstick with someone who has it.

In addition, if you or your partner gets cold sores on the mouth, the herpes simplex virus-1 can be transmitted during oral sex and cause herpes in the genital area.

Herpes simplex virus-1 also can spread if a person touches the cold sore and then touches a mucous membrane or an area of the skin with a cut on it. Mucous membranes are the moist, protective linings made of tissue that are found in certain areas of your body like your nose, eyes, mouth, and vagina. So it's best to not mess with a cold sore — don't pick, pinch, or squeeze it.

Actually, it's a good idea to not even touch active cold sores. If you do touch an active cold sore, don't touch other parts of your body. Be especially careful about touching your eyes — if it gets into the eyes, HSV-1 can cause a lot of damage. Wash your hands as soon as possible. In fact, if you have a cold sore or you're around someone with a cold sore, try to wash your hands frequently.

If they aren't taken care of properly, cold sores can develop into bacterial skin infections. And they can actually be dangerous for people whose immune systems are weakened (such as infants and people who have cancer or HIV/AIDS) as well as those with eczema. For people with any of these conditions, an infection triggered by a cold sore can actually be life threatening.