Cold sores are usually caused by the herpes simplex 1 virus. More than 80% of people have this virus permanently living dormant in their bodies. Strong immune systems are usually able to contain the virus from becoming active, but when an infected person is exposed to certain factors, the virus can be triggered and cause an outbreak on the skin.

Common cold sore triggers:

Weather: Exposure to cold weather and wind can dry and chap the lips as well as cause dryness around the mouth, triggering cold sores to form. Basking in the sunlight or using a tanning booth can often trigger cold sores as well, especially if the lips become sunburnt.

Fever and sickness: Any type of sickness or infection that weakens the immune system reduces the body's ability to fight off the cold sore virus.

Emotional and mental stress: High levels of stress can also lower the immune system and cause cold sore outbreaks. A weakened immune system also prolongs the healing period.

Injury or Irritation to the lips: Any type of injury or trauma to the lips, such as a burn from hot foods or beverages, a cut, or irritation caused by a dental appointment can make the lips vulnerable to a cold sore infection.

Menstrual periods: Many women only get cold sores during their menstrual cycle. This is believed to be caused by an imbalance of hormones which can have an effect on the function of the immune system.

The herpes simplex 1 virus is a permanent condition with no cure. Because most of us harbor the virus in our bodies, any of these triggers can cause a cold sore outbreak at any time. Everyone's body reacts differently to these triggers and it is important to understand which particular ones cause your cold sores so that you can better prevent outbreaks.