Before diving into what causes a cold sore and what can be done to prevent it, let’s take a look at why you may be experiencing outbreaks of colds sores in the first place.

Cold sores are a type of herpes infection that comes in the form of painful blisters which appear around the mouth and lips. They can result in significant irritation, pain, discomfort, and worry for whoever is affected.

What is the virus behind Cold Sore outbreaks?

Cold sores are caused by herpes simplex virus type 1 (HSV-1), an extremely common virus that is estimated to be carried around in about every seven out of ten people. Most people come into contact with it before the age of 10, but often find that they don’t experience symptoms (outbreaks) before they reach puberty. Once you have been infected by the virus you then carry the virus with you for the rest of your life.

The herpes simplex virus is passed from one person to another by saliva or direct skin contact. After the infection, the virus remains dormant (inactive) in the nerves of the face. For some people the virus always remains inactive, while for others the virus becomes active again causing outbreaks of cold sores.

What causes Cold Sore outbreaks?

While we have established what the virus behind cold sore outbreaks is, we have not looked into what exactly is causing the outbreaks and what can be done to prevent them.

The truth is that there is not a single reason for an outbreak of cold sores, but rather a few factors that can make you more prone to a cold sore breakout (or flare-up). These reasons include:


  • Stress can cause the weakening of your immune system
  • This gives the inactive HSV-1 a chance to launch an outbreak
  • When you feel stressed, make sure to breathe deeply and find time to relax


  • Being tired can make you more prone to cold sores as similar to stress it weakens your immune system
  • Getting rest is important to prevent further cold sore outbreaks

Cold weather:

  • Facing the cold may mean also mean facing a cold sore flare-up
  • Try to familiarise yourself with the cold weather that can dry out lips and trigger your cold sores

Excessive sunlight:

  • Unprotected sun exposure can trigger cold sores
  • Make sure to use SPF lip balm and try to avoid excessive sunlight exposure during the summer months

Weakened immune system:

  • You are more likely to experience an outbreak when your immune system is weakened
  • When you feel a cold, fever, or the flu approaching, make sure to take the right precautions as soon as possible

Hormonal changes:

  • For women, hormonal changes during the menstrual cycle can cause a cold sore flare up
  • Make sure to pay close attention for signs of a cold sore so you can bring it under control quickly treat it early

How to best get rid of Cold Sores quickly?

There are a number of over-the-counter (OTC) solutions available to treat your cold sores. Pharmacies in the UK usually sell antiviral creams which contain the antiviral Valaciclovir. Sometimes a GP will prescribe Valaciclovir in a tablet form to bring the cold sore more quickly and effectively under control. The usual dose for cold sores is 2000mg of Valaciclovir at the first sign of symptoms, followed by another 2000mg 12 hours later. The treatment should be started at the first sign of a cold sore (tingling, itching, or burning sensations) for best effectiveness.

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