What does a cold sore look like?

Cold sores will start to manifest as a burning, itching or tingling sensation at the site of the outbreak.

During the initial stages of the outbreak, the blisters will be small, and filled with clear fluid, and will often cluster together at the site of the outbreak. This may cause some oozing but the blisters will eventually burst and scab over, indicating that the outbreak is ending.

An untreated cold sore can last up to two weeks, though most outbreak cycles will complete within seven to ten days.

Cold sores outbreak tends to have five distinct stages of outbreak.

1) The tingle stage

The first stage, also the ‘tingle stage’ is where the first symptoms of a cold sore are felt, before the cold sore appears. This stage is usually accompanied by burning, itching or tingling feeling around the area where the cold sore will develop.

2) The blister stage

The second stage is where the blisters begin to form. A small number of clear fluid-filled blisters will start forming and clustering together. At this stage some pain might be felt as the blister forms.

3) The ulcer stage

The ulcer stage is where the blisters burst and create an open sore (ulcer). The sore might look red and irritated and it is the most painful stage of the outbreak.

4) The scabbing stage

At this stage, the sore will dry out and form a scab, indicating that the healing process has started. The scab will start shrinking, but the scab might crack and cause bleeding. You might feel the itching sensation around the scab as it heals. This is why it’s important not to touch or try to remove the scab, as it will slow the healing process down.

5) The healing stage

The final stage of the outbreak, the healing stage is when the scab will start to come off on its own. There might still be some flaking or residual swelling but the cold sore is now almost fully healed.

Cold sores are the most contagious during their ulcer stage, but they remain contagious through all five stages to various degrees. Make sure you do not have skin-to-skin contact with anyone during this time and avoid sharing eating utensils.

Warning: Do not kiss infants or very young babies if you have an outbreak as this could cause neonatal herpes, which are dangerous to infants.

See below for some examples of what cold sores look like at different stages of the outbreak:

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Sometimes, cold sores can be confused with other types of infections and blisters that have similar properties to cold sores, but are in fact entirely different.

Angular cheilitis is a very common skin condition that also causes painful, cracked sores in the corners of the mouth. Unlike cold sores, which can appear anywhere around the lips or face, angular cheilitis appears only on the corners of the mouth, and they are not contagious.

Angular cheilitis is not caused by a virus, but is instead triggered by a fungal or bacterial infection, and unlike the cold sores, it does not produce a cluster of small blisters.

Both cold sores and shingles are infections caused by a herpes virus. However, while cold sores are caused by herpes simplex type 1 (HSV-1), shingles are caused by the herpes virus Varicella-zoster (VZV), which also causes chicken pox. It is rare for shingles to develop around the mouth, though they can appear inside the mouth, also called oral shingles, and tend to affect half of the face.

Shingles tend to manifest as a rash, rather than a small cluster of blisters. If you notice a more localised presence of small blisters on the lips and around the mouth, it is more likely to be a cold sore than shingles.

Mouth ulcers are blisters that form inside the mouth and have a range of causes and triggers. While cold sores can appear inside the mouth, it is very rare for them to do so. Mouth ulcers also tend to form as a single blister inside the mouth, rather than a cluster. If you notice a blister inside your mouth, in most cases (except in very rare cases) it won’t be a cold sore, however be aware that more than one mouth ulcer at the same time could be a sign of a number of different conditions, as well as a weakened immune system. If you do notice several mouth ulcers, speak to your doctor for diagnosis and treatment.

The most likely place you will see a cold sore would be around the mouth, especially the lips, though they can be also found on:

• nose
• cheeks
• chin
• eye
• inside the mouth (in rare cases)
• other places if transferred from an outbreak

HSV-1 can also infect the eyes, causing an outbreak in or around the area, which can be extremely painful.

An active cold sore can also infect an eczema outbreak if it comes in contact with it. This is known as eczema herpeticum. Unlike a cold sore, this particular infection will not go away without treatment, and you will need an antiviral medicine (such as Aciclovir) to treat it.

This is why it is important to not touch a cold sore and then touch other areas of your body, as infection can spread quickly to other parts of the face and body.

Cold sores can be visually identified and diagnosed by your doctor. In cases where another condition is suspected or a cold sore appears atypical, the doctor will take a sample from the cold sore and send it to a laboratory for HSV testing.

Most often, however, your doctor will be able to recognise and diagnose the cold sore just by looking at it.

In most cases, cold sores resolve without treatment within one to two weeks, but there are a number of treatments your doctor can prescribe to speed up the healing process and alleviate the symptoms. Some of the most prescribed medications include Aciclovir, Valaciclovir (Valtrex), Famciclovir (Famvir) and Penciclovir, among others.

You should let your doctor know if your cold sore is long lasting or severe, if you experience eye discomfort while you have an outbreak, or if your cold sores return very often.