Cold sores are tiny blisters that usually cluster around the lips and are caused by the herpes simplex virus, according to the Mayo Clinic. Also known as fever blisters, they usually occur on a reddened patch of skin accompanied by pain or tingling. Cold sores usually last 10 to 14 days. The infection, sometimes called herpes labialis, is rarely serious though it can cause complications such as severe infection and blindness.
Causes of the Initial Infection
Most cold sores are caused by herpes simplex type 1, according to the Mayo Clinic. However, herpes simplex type 2, which normally causes genital herpes, can also cause cold sores in some cases. These viruses are usually spread by physical contact with someone who has an active sore. It can take up to 20 days after exposure for the first sores to appear but sometimes the initial infection causes no symptoms at all. Kissing, oral sex, and sharing razors, towels, lipstick, dishes, or eating utensils can spread the infection. The cold sores are infectious from the time they first appear until the blister has completely disappeared and healed. Even after the blister has subsided, it is still possible to spread the virus for a short time, according to the Mayo Clinic.
Causes of Recurrent Outbreaks
Once the initial outbreak has cleared up, there is still a risk of recurrent outbreaks, according to the Mayo Clinic. The herpes virus doesn't leave the body after the initial illness. Instead it lies dormant in the skin's nerve cells and can re-emerge as an active outbreak of new cold sores around the site of the first outbreak. This can happen at any time and can occur repeatedly over many years. The causes of these recurrent outbreaks are not always known but infection, fever, stress, tiredness, cold weather, menstruation, pregnancy, tooth extractions and sun exposure can sometimes trigger them. In some people, certain foods or drugs can also trigger an outbreak, according to TeensHealth from Nemours.
Risk Factors for Complications
Some people are at a greater risk for serious complications from a herpes infection, according to the Mayo Clinic. People with active sores should avoid contact with infants, people with eczema, or anyone who has an impaired immune system from cancer, HIV or an organ transplant. Because these people cannot easily fight off the herpes infection, it can develop into a life-threatening, more generalized infection. Herpes infections can also lead to secondary bacterial skin infections, which can be serious, and to infections of the eye that can cause blindness, according to MedlinePlus.
