Cold sores form on lips because of an infection by the herpes simplex virus, which gets into the body through a cut or scratch in the mouth or nearby skin, WebMD states. Contact with a cold sore or with HSV-infected fluid spreads the infection.
To reduce the risk of infection, one should avoid sharing bodily fluids and bringing items used by others to the infected area, WebMD cautions. Avoiding a kiss with an infected individual and avoiding his utensils, cups, razors or other items that he may have brought into contact with his mouth helps to prevent cold sores.
Once infected with HSV, the individual can alleviate symptoms and reduce the likelihood of spreading the infection by treating the area with lip balm and sunscreen, avoiding sources of stress and disease, and making sure not to touch the sore, WebMD advises. Lip balm and sunscreen are helpful in minimizing the effect of sunlight, which can cause an outbreak of cold sores in infected individuals. Emotional stress and common types of disease, such as a cold or flu, may cause a sore outbreak. Persons suffering from cold sores should avoid touching the sore, and they should wash their hands often to avoid spreading the disease.