A risk factor is something that increases your likelihood of getting a disease or condition.

It is possible to develop cold sores with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing cold sores. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.

The viruses that cause cold sores are easily spread. They come out of the skin and are “shed” from the site of the cold sore for 1-2 days before the sore appears. Then they are in the fluid of the cold sore blisters. Although cold sores typically form in response to stress or illness, they can sometimes form without an identifiable trigger.

Risk Factors for Becoming Infected With Herpes Simplex 1 Virus

Exposure to Someone With Cold Sores

Herpes simplex virus type 1 (HSV-1) can be spread by close contact with someone who has a cold sore or by using items contaminated with the virus. Kissing or sharing personal items, such as razors, towels, or eating utensils, with a person who has a cold sore will increase your risk of getting HSV-1. The virus you have can also be spread to the genital area of another person by having oral sex. People with cold sores should not perform oral sex on their partners.


Infants and young children (up to three years old) have an increased risk of being exposed to HSV-1.

Risk Factors for Developing Cold Sores

Exposure to Sunlight

Exposure to sunlight or other ultraviolet light is a common trigger for the formation of cold sores.

Physical Stress and Illness

Stress on the body due to illness or excessive exercise can weaken the body’s immune system and lead to an outbreak of cold sores. Common examples of stress or illness include:

  • Infection, fever, or ]]>cold]]>
  • Physical injury
  • Dental surgery
  • Menstruation
  • Medication (such as steroids) or illness (such as ]]>HIV]]> ) that suppresses the immune system
  • ]]>Eczema]]>
  • Excessive exercise

Emotional Stress

Cold sore outbreaks commonly occur during times of emotional stress. The type of stress that activates cold sores is typically negative stress, instead of stress due to positive or normal life-changing events.