What are cold sores?

Dr Lisa Beckett
March 2022

HSV affects up to 90% of adults but it doesn't have to be so unpleasant.

Everyday health

Cold sores are small blisters on lips and around the mouth that are caused by Herpes Simplex Virus (HSV). Around 90% of adults are infected with HSV in their lifetime, but only a third experience symptoms.

HSV is stored in your body and may flare up at any time, usually at times of stress and illness. Most cold sores are caused by HSV 1. HSV 2 is more likely to cause genital herpes although there is overlap between the two.

What symptoms does HSV cause?

Cold sores usually start with itching and tingling. A day or two later blisters appear - these may involve pain and heat and can last for a few days before bursting and crusting over. It takes about 10 days for the cold sore to resolve.

Are cold sores serious?

The majority of the time cold sores are annoying but get better and resolve with time. In some cases, especially if you have a weakened immune system (such as chemotherapy or long term steroid use), symptoms can be more severe and spread. While it’s unlikely to occur some cold sores can be more complicated.

If you experience any of the following please see your regular GP immediately:

  • Bacterial infection: pus, redness and sometimes fever
  • Symptoms involving eyes: HSV can cause ulcers to eyes that can permanently damage sight so it is important to see your doctor as soon as possible

Are cold sores contagious?

Very. They spread by contact with saliva or infected cells. You are most contagious when the blister is first starting but cold sores are contagious at all stages of the infection. It is very important to avoid close contact including kissing when you have symptoms.

To prevent spread do not share toothbrushes, drinking glasses, towels or other personal items. It is also very important not to engage in oral sex when you have a cold sore as this can result in genital herpes.

What can I do about them?

Anti-viral medication can help shorten the duration of cold sores and even prevent them from appearing. Taken early it can significantly help symptoms so it’s best to have on hand just in case. Topical treatment can be effective in some people but most find oral anti-virals work best. Have a chat to us at Candor about how we can help.


Herpes simplex (cold sores): Causes and Treatment — DermNet. (n.d.). Retrieved from https://dermnetnz.org/topics/herpes-simplex

Herpes Simplex Virus Infections. Therapeutic Guidelines Ltd (eTG March 2021 edition). Published November 2015. Amended December 2020.

Is medical cannabis right for you?

Candor provides a free screening before your initial consultation that will help determine your eligibility.

Start free screening

Get the pill online

Whether you know exactly what you want, or its your first time and you need some direction, Candor can help.

Learn more