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Cold sores (fever blisters) are a common viral infection. They are tiny, fluid-filled blisters on and around your lips. These blisters are often grouped together in patches. After the blisters break, a crust forms over the resulting sore. Cold sores usually heal in two to four weeks without leaving a scar.

Who can get cold sores and why?

Kissing is a common form of transmission of Herpes Simplex Virus (HSV-1), and estimates suggest that about half the population has been infected with HSV. But not everyone who has been infected will develop cold sores. There’s no cure for HSV infection, and the blisters may return. Antiviral medications can help cold sores heal more quickly and may reduce how often they return.

Cold sore triggers

  • Stress
  • Fatigue
  • Viral infection or fever
  • Changes in the immune system
  • Exposure to sunlight and wind
  • Hormonal changes, such as those related to menstruation

Risk Factors

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

  • HIV / AIDS
  • Severe burns
  • Eczema
  • Cancer chemotherapy
  • Anti-rejection drugs for organ transplants

Did you know?

Cold sores are most contagious when oozing blisters are present. But you can transmit the virus to others even if you don’t have blisters.


  1. Tingling and itching around lips for a day or so before a small, hard, painful spot appears and blisters erupt.
  2. Blisters: Small fluid-filled blisters typically break out along the border. Cold sores can also occur around the nose or on the cheeks.
  3. Oozing and crusting: The small blisters may merge and then burst, leaving shallow open sores that will ooze fluid and then crust over.


  • Apply a cold sore ointment. Docosanol (Abreva) is an over-the-counter cream for cold sores. It must be applied frequently and may shorten an outbreak by a day.
  • Try other cold sore remedies. Some over-the-counter preparations contain a drying agent, such as alcohol, that may speed healing.
  • Use lip balms and cream. Protect your lips from the sun with a zinc oxide cream or lip balm with sunblock. If your lips become dry, apply a moisturizing cream.
  • Apply a cool compress. A cool, damp cloth may reduce redness, help remove crusting and promote healing.
  • Apply pain-relieving creams. Over-the-counter creams with lidocaine or benzocaine may offer some pain relief.

When to see your Doctor

  • You have a weakened immune system
  • The cold sores don’t heal within two weeks
  • Symptoms are severe
  • You have frequent recurrences of cold sores
  • You experience irritation in your eyes

Rxnet is a virtual pharmacy network that helps plan sponsors optimize their drug plan design to obtain cost efficient solutions for their plan members. We also work with clients to provide access to our member pharmacies through text refills and online refills. This article was provided by Samantha Thai, PharmD from McMaster Health Campus Pharmacy.

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