Cold Sore

Cold sore causes and triggers

3 min read

Cold sores are a common condition caused by a virus, commonly the herpes simplex virus type 1 (HSV-1), and sometimes less commonly, the herpes simplex virus type 2 (HSV-2)[2]. Cold sores are very contagious and can be spread even if no blister is visible.

Once you have caught the virus, certain factors can trigger a new cold sore outbreak. We’ll look at what can trigger a cold sore outbreak.

  • The cause of a cold sore and what triggers an outbreak are different
  • Cold sores are caused by the HSV-1 virus
  • An outbreak can be triggered by a number of factors including your health, stress and weather conditions

In this article:

  • Cold sore causes
  • What causes the first cold sore?
  • Cold sore triggers
  • Why do you keep getting cold sores?

What causes the first cold sore?

You can catch the virus that causes a cold sore, sometimes called a fever sore, by being in contact with someone who has the HSV-1 virus.

Contact is one the main causes of a first cold sore – whether it’s through bodily contact, such as kissing or an exchange in bodily fluids, such as sharing glasses and straws.

Any intimate or personal contact with someone with the virus – and especially with an active cold sore – can trigger someone who has never had a cold sore before to have an outbreak.

The virus that causes a cold sore is contagious even before a blister develops. Young babies – under 8 weeks old – are most at risk of getting cold sores as their immune system hasn’t fully developed. If a parent has a cold sore they should be careful not to kiss them or put their pacifier in their own mouth[1].

Cold sore triggers

If you have developed a cold sore in the past, it’s likely to return again. People with the HSV-1 virus usually get one or two outbreaks a year, with 5% getting them more than 5 times a year[1].

There are a number of cold sore triggers that can lead to you developing one.

These triggers include[2]:

  • Sun exposure: Take precautions in the sun. Ensure you apply lip sunscreen, use a wide-brim hat that protects the face and stay in the shade where possible.
  • Being in the cold: The dry air and colder temperatures can cause your lips to become dry and cracked. This can make them vulnerable to cold sore blisters. Protect your face, apply a soothing balm regularly and drink plenty to stay hydrated.
  • Having a weakened immune system: If your body is already fighting another virus such as flu or a cold, it leaves it susceptible to cold sore outbreaks.
  • Stress: Stress can affect you in many different ways and when feeling stressed, it can have a huge impact on our immune system. Try and find helpful ways to relax, such as meditating to help reduce stress.
  • A change in hormone levels: Hormone imbalance brought during a menstrual cycle can cause the virus to activate and cold sores to appear just before or after a period.

While many people with cold sores often associate an outbreak with their diet, there’s little evidence to suggest that a high intake of caffeine or alcohol can cause an outbreak.  Vaccines do not cause cold sores either[3].

Why do you keep getting cold sores?

When the HSV-1 virus has been contracted, the virus stays in the body for the rest of your life. It remains dormant until triggered and a cold sore develops.  It usually forms on or around the lips, or even between lips and the nasal area.

Avoiding common triggers and protecting and caring for your lips can help reduce the chances of an outbreak.

While the HSV-1 virus is not curable, cold sores are treatable. There are a number of ways you can treat a cold sore, such as by taking care to avoid the triggers we mentioned above, or by using creams or patches to protect and cover the cold sore.


Mederma® Cold Sore Discreet Healing Patch

  • Hydrocolloid gel technology
  • Helps heal cold sore fast
  • Helps reduce scab formation and contamination

Buy today


Cold sores are caused by the HSV-1 virus, usually contracted after coming into contact with someone who has an active cold sore.  An outbreak can be triggered by everything from weather to your health. While there’s no cure, there are treatments that shorten the length of an outbreak.


Did you like this article? Please let us know if you found this article useful.
Back to Top