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woman nervous about cold sores touching her lip
woman looks nervous about cold sores touching her lip

Fever Blister Vs. Cold Sore

What is a fever blister exactly? The answer might surprise you – it’s simply a cold sore. A fever blister and a cold sore are one and the same. If you’ve ever had a blister on your lip, chances are it’s a result of the herpes simplex virus and your fever blister was in fact a cold sore.

So why the confusion? Cold sores have been called fever blisters in the past because they often appeared when someone had a fever. But fever blisters are caused by the exact same virus as cold sores, because they are the same thing.

Discover how to treat and prevent fever blisters with our top lip care tips.

Fever Blister

What Is a Fever Blister?

 If you’re asking yourself what a fever blister is, the answer is simple – it’s a symptom of a virus that infects the mouth area. This virus attacks cells and, as a side effect, it creates an area of inflamed sore skin, which we call a fever blister or a cold sore.i

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What Causes a Fever Blister on Your Lip?

 In addition to being called fever blisters or cold sores, these blisters are often called oral herpes because they are caused by the herpes simplex virus 1 (HSV-1). This common viral infection affects around two thirds of adults aged 50 and over according to the World Health Organization, but not everyone will show the telltale symptom of blisters on their lips.ii

Fever Blister

Where Do You Get Fever Blisters?

The blisters associated with cold sores appear on the lips or the edges of the lips. If, however, the herpes simplex virus (HSV-1) is passed to other parts of the body, such as the nose, eyes or genitals, you may experience fever blisters there, too.

Fever Blister

What Does a Fever Blister on Your Lip Look Like?

A fever blister on your lip will appear as a small area of red, inflamed skin that may feel sore. A blister will then form, and may break apart and weep clear liquid. After a few days, the fever blister will be covered by hard crusts or scabs. More than one blister is likely, with fever blisters often grouped together in patches. Fever blisters heal without leaving a scar.

Fever blister on lower lip

Are Fever Blisters Contagious?

Fever blisters are highly contagious and can be spread easily. The HSV-1 virus is most contagious when you are showing symptoms of a cold sore – from first experiencing the tingling, itching or burning sensation that suggests a fever blister is coming right through the period when the blister is visible and hasn’t completely healed.iii

To avoid passing the virus to others, you should stick to a strict hygiene regime and avoid kissing and sharing objects such as eating utensils and cosmeticsiv. And, if you do feel the tingle, make sure you have a tube of Abreva® Cream with you, so you can slow the virus and possibly prevent a full fever blister or cold sore from developing.

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How Long Will a Fever Blister on My Lip Last?

A blister or cold sore on your lip may take up to two weeks to fully heal. Symptoms normally begin with a tingling, itching or burning sensation. It later develops into a blister, may weep clear fluid and then scab over.v You can reduce the healing to just a few days using Abreva® Cream when used at the first sign.


Are Fever Blisters Serious?

Fever blister complications are uncommon. Most people who are infected with the HSV-1 virus may suffer with outbreaks of blisters from time to time, but many people don’t show any symptoms at all.

As a blister can break open, you are at risk of bacterial infection if you keep touching the area and don't keep your hands and face clean. If the virus spreads to the eye, medical help should be sought as repeated infection can cause scarring and injury, which may result in vision problems or blindness. Babies and those with weakened immune systems may catch a widespread herpes infection if exposed to a cold sore, which can affect vital organs, including the spinal cord and brain. Eczema sufferers are at risk of developing a dangerous condition called eczema herpeticum if they come into contact with cold sores. This means the infection spreads throughout their body, leading to long-term scarring, blindness and sometimes organ failure or


Can I Prevent a Fever Blister?

Once you are infected, the HSV-1 virus never leaves your body. It lies dormant in the nerve cells in your skin until a trigger – such as a cold or flu, excessive sunshine, cold weather or stress – causes the virus to replicate uncontrollably, causing the telltale symptom of a cold sore or fever blister on your lips.vii

You can try to protect yourself against outbreaks by always drinking lots of water, getting plenty of rest, having your annual flu vaccination and managing cold sore triggers such as stress, fatigue, cold or excessive sunlight.

Cream on finger

Fever Blister Treatment

There is no cure for the herpes simplex virus nor is there a vaccine, but there is effective fever blister treatment. You can treat the blister or the area where you feel the pre-blister tingling with Abreva® Cream, which will help prevent the virus from replicating and causing more inflammation or damage. It contains the only FDA-approved non-prescription ingredient proven to reduce your cold sore healing time.

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