20 % of people regularly get cold sores. Genetics has everything to do with this unwanted sore.
The herpes simplex virus type 1 (HSV-1) is found in 9 out of 10 people.

University of Edinburgh in Scotland analyzed thousands of genes. This was done to find the genes to responsible for making the protein that prevents the virus from becoming active. Blood samples were then researched, after identifying multiple genes. The study was of 20 people. The gene IL28B, was consistently mutated in people who got sores.The mutated gene is unable to produce the necessary protein. The people affected are then left with a weak immune system, unable to help fend off the sores."The insight suggests a possible treatment route not just for cold sores but other infections caused by HSV-1", said Dr. Jürgen Haas. In common cold sores acyclovir is used. acyclovir is the common treatment. unfortunately the same virus also causes more severe infections of the brain, the eyes and the genital tract. When acyclovir is ineffective a treatment involving IL28B might be used.