Cold sores Symptoms & Causes

LIke ThisLIke ThisLIke ThisLIke ThisLIke This

What are cold sores?

Cold sores, also called oral herpes or fever blisters, are small blisters around the mouth (including lips, chin, and cheeks) or in the nostrils. Episodes of the cold sores usually last no longer than two weeks. They are contagious.

What causes cold sores?

Cold sores are caused by the herpes simplex virus. The most common strain of the virus is herpes simplex virus 1. The herpes simplex virus is not curable, but may lay dormant for long periods of time. Hot sun, cold wind, a cold, or a depressed immune system can cause an outbreak of herpes simplex virus symptoms. Oral herpes is transmitted through:

  • direct contact between the contagious area and broken skin (a cut or break) and mucous membrane tissue (such as the mouth or genitals)
  • contagious whether or not symptoms are present

Are cold sores common?

Type 1 herpes virus infects more than half of the people in the United States by the time they reach their 20s.

What are the symptoms of cold sores?

Some children and adults never experience any symptoms with the first attack; others have severe flu-like symptoms and ulcers in and around the mouth. While symptoms may vary child-to-child, they may include:

  • tingling of the lips
  • a small blister or cluster of blisters on the lips and mouth that enlarge, burst, then crust over
  • itching and irritation of the lips and mouth
  • soreness of the lips and mouth that may last from three to seven days
Boston Children’s is so much more than a hospital—it’s a community of researchers, clinicians, administrators, support staff, innovators, teachers, patients and families, all working together to make the impossible possible. ”
- Sandra L. Fenwick, President and CEO

Boston Children's Hospital
300 Longwood Avenue, Boston, MA 02115
For Patients: 617-355-6000
For Referring Providers: 844-BCH-PEDS | 844-224-7337

Close