Why Do We Get Cold Sores?

There are several causes of cold sores, but almost all of them are related to problems that can be easily solved.
Why Do We Get Cold Sores?

Written by Edith Sánchez

Last update: 27 May, 2022

Cold sores are lesions that appear on the corner of the lips and whose medical name is stomatitis or angular cheilitis. This disease is also called cheilosis, commissural cheilitis, or commissural stomatitis.

These small wounds have the form of a fissure or crack and, in all cases, they appear at the junction of the lips. The lesion appears covered with a whitish membrane. They can be unilateral, that’s to say, they only appear on one side of the mouth, or bilateral, when they’re present on both corners of the mouth.

But why do cold sores appear?

Who suffers from cold sores?

A woman with cold sores.

The presence of cold sores is quite common and, in fact, specialists believe that almost everyone suffers from this discomfort at least once in their lives. However, if there’s one group in particular that stands out for the presence of cold sores, it would be children.

In children, they occur especially during the appearance of the first teeth or when they use pacifiers a lot. They’re also frequent in the elderly and in those who have dental problems.

Other groups in which cold sores occur frequently are people who have deep creases in the corners of the mouth. Another group is those who suffer from diabetes, cirrhosis, anemia, immune system deficiencies, vitamin C deficiency, or poor nutrition.

Overall, they have multiple causes but are almost always caused by the presence of fungi or bacteria.

What are the types of cold sores?

The first classification of cold sores or angular cheilitis has to do with their recurrence. If they occur suddenly and with stronger symptoms, we’re facing an acute case. If they appear and disappear several times throughout life and there are painful fissures, it’s called a chronic condition.

From the point of view of the cause of cold sores, the Revista Cubana de Estomatología in its article Queilitis. The bibliographic review explains that these are classified into three types of cheilitis:

  • Microbial: It’s due to the presence of microorganisms growing in the labial commissures.
  • Contact: It’s a form of contact allergy and occurs when there is contact with the allergen.
  • Solar: It appears in people who are very sensitive to the sun and generally occurs from an early age. It’s also caused by extreme temperature changes.

What are the symptoms?

The main symptom when cold sores appear is redness and peeling at one or both corners of the lips. Most commonly, small erosions are covered by a white or yellow pseudomembrane form.

The affected person feels some tightness in that area when moving their mouth. Also, they feel pain when they open their mouth or eat certain foods, especially if they’re acidic. They feel a burning sensation and increased sensitivity in the area. In the most severe cases, there’s bleeding and crusting.

Why do cold sores appear?

Cold sores on a tongue.

The reasons for the appearance of cold sores are varied. There are three main groups of triggers, according to data published in a StatPearls trial:

Local triggers

These are related to the changes that occur in the mouth area. The main local factors that cause the appearance of cold sores are the following:

  • Lack of teeth or edentulism: when a person doesn’t have any teeth, deeper grooves form in the corner of the lips and this facilitates the eruption of cold sores
  • Mismatches in prosthesis or dental appliances
  • Accumulation of saliva in the corner of the lips
  • Contact with an allergen
  • Dry lips
  • Oral candidiasis
  • Inadequate habits: mainly, frequent wetting of the lips or biting the corners of the mouth

Systemic triggers

These have to do with other diseases that may be present. Among them, we find the following:

  • Nutritional or vitamin deficiency: in particular, lack of vitamins A, B, or C and iron or zinc deficiency.
  • Depression of the immune system: low defenses contribute to the appearance of cold sores.
  • Systemic diseases: e.g. diabetes, impetigo, cirrhosis, anemia, etc.

Environmental triggers

These are related to the environment. Among them are:

  • Extreme temperatures: especially, when changing from one to another in a short period of time.
  • Stress, anxiety, or emotional problems: they affect the proper functioning of the immune system.
  • Traumas: if there’s a blow, burn, or other types of injury to the corners of the mouth, it’s easier for them to appear.

What to do if you have a cold sore

A woman smiling.

It’s important to note that cold sores are contagious since they’re an infection. They’re transmitted from one person to another by kissing, or by sharing items that the affected person has put in their mouth.

Therefore, the first step after determining that you have cold sores is to take extreme precautions to minimize the risk of someone else getting it. This means: avoid kissing and using the same towel in the bathroom, as well as sharing glasses or cutlery.

Of course, we recommend medical consultation. The professional is the only one who can reliably determine the causes of cold sores and thus help to treat them properly.


All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.