Pharmacy Corner
Cold Sores: What You Need to Know How do I know if I have one?

Example of what a cold sore looks like:

Cold sore
Cold sore

Signs and symptoms

  • Cold sores are most common on the lips and mouth
  • Tingling, burning or itching starts about 24 hours before the cold sore appears – this is called the “prodrome phase”
  • Cold sores look like one or a small group of painful blisters on one side of the lip or mouth area with a red base
  • Blisters eventually break and leak a clear fluid that eventually starts to crust or scab
  • Without treatment, healing occurs without scarring in 1-2 weeks
  • Some people may be infected with the virus but never show any symptoms


Most adults are infected with the virus but only 20% of people who are infected with actually get cold sores. That means about 80% of adults with the virus are unaware they are even infected and can still pass the infection to others.5

Cold sore checklist:3

Likely a cold sore

Possibly NOT a cold sore

  • Tingling, itching or burning in the area before the sore develops

  • Appearance of fluid filled blisters on the lip

  • Blisters have broken, leaked a clear fluid

  • Crust or scab formation

  • Complete healing in 7-14 days

  • Come about after long sun exposure

  • Having honey-coloured crusts

  • Sores on the inside of the mouth or lips

  • Sores spreading to other areas of the body

  • Lasts longer than 14 days

  • Sore is very swollen, red, has pus or blood

  • Other symptoms like fever, fatigue, nausea/vomiting

  • No history of ever having cold sores before