About 90 percent of adults worldwide — even those who've never had symptoms of an infection — test positive for evidence of the virus that causes cold sores.

People who have weakened immune systems are at higher risk of complications from the virus. Medical conditions and treatments that increase your risk of complications include:

  • HIV/AIDS
  • Eczema
  • Severe burns
  • Cancer chemotherapy
  • Anti-rejection drugs for organ transplants
May. 23, 2012

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