Initial Infection

• Primary infection of herpes simplex I usually occurs in early childhood.it's cold! image by Renata Osinska from Fotolia.com
  
  The virus that causes cold sores originally enters your body between the ages of 3 and 5, usually by kissing an infected relative.
  
  

Function

• The UV rays of the sun may suppress the immune system or disrupt the nerve cells which harbor the virus in its latent phase.The girl in a wood. image by Yuri Bizgaimer from Fotolia.com
  
  Herpes simplex I lies dormant in the skin or nerve endings, but aggravating factors such as a sunburn may cause the virus to move down the nerve endings and up to the skin, usually emerging on the lip or face.
  
  

Theories

• Use a sunblock with a sun protection factor of at least 15 if the sun causes cold sores to develop on your lips or face.sun burst image by Kimberly Reinick from Fotolia.com
  
  Ultraviolet radiation from the sun may temporarily suppress the immune system, particularly during the months of July and August, according to an investigation performed by researchers at the Kobe University Graduate School of Medicine in Japan.
  
  

Insight

• You may have a sensitivity to the ultraviolet rays of the sun which causes cold sores to break out on your lips or face.suntanned girl walking on the beach in white bikini image by Olga Sapegina from Fotolia.com
  
  The investigation also questioned the possibility that sunlight causes reactivation of the herpes simplex virus I within the neural ganglia, a group of nerve cells which harbor the virus during its latent phase.
  
  

Prevention

• A pigment-rich lipstick or a lip pomade with sunscreen protects the lips when you go out in the sun.lips image by DXfoto.com from Fotolia.com
  
  Try to maintain a healthy lifestyle which includes getting enough sleep and eating nutritious foods. When going out in the sun, use a sunblock of at least 15 SPF, but preferably 25 SPF, generously applying it to the area around your lips. You may also use a richly pigmented lipstick or a colorless lip pomade that contains sunscreen.