Impetigo vs Cold Sore: How to Tell the Difference

Two crusted sores around the mouth can look very similar, but they have different causes. A cold sore is caused by the herpes simplex virus, while impetigo is a bacterial skin infection.

Knowing the difference matters because the treatments are different. Antiviral medicines are used for cold sores, while impetigo may need antibacterial treatment. Using the wrong treatment may delay getting the right care and, with impetigo, could allow the infection to spread to other people.

This guide explains the main differences between impetigo and cold sores, why they can be confused, how they are treated in the UK, and what to do if you are not sure which one you have.

Key things to know

• Cold sores are caused by the herpes simplex virus, most often HSV 1.
• Impetigo is caused by bacteria, usually Staphylococcus aureus and sometimes Streptococcus pyogenes.
• Impetigo is not a type of herpes, and herpes is not a type of impetigo.
• Impetigo is particularly common in children aged two to five, although adults can also develop it.
• Both conditions can spread to other people, but they spread in different ways and have different guidance around contact with others.
• Other skin conditions can look similar, including angular cheilitis and hand, foot and mouth disease.
• If you are unsure what is causing a sore, or if it is spreading or getting worse, speak to a healthcare professional for an assessment.

What Is a Cold Sore?

A cold sore is caused by the herpes simplex virus, usually HSV 1. Many people first come into contact with HSV 1 during childhood and may have few or no symptoms at the time. Once the virus enters the body, it remains there and can become inactive for periods before becoming active again.

When the virus reactivates, it can travel along a nerve to the skin. This is why cold sores often appear in a similar area each time.

A cold sore often starts with tingling, itching or a burning feeling several hours before the sore becomes visible. This early stage is known as the prodromal stage and can be a useful sign that a cold sore is developing. Starting an online cold sore assessment early may allow a suitable antiviral treatment to be considered.

Small, fluid filled blisters can then appear, often in a group around the lip or mouth. The blisters may break, become sore or wet, and then form a crust as they heal.

Commonly reported triggers include sunlight, stress, tiredness, illness and hormonal changes, although triggers can vary from person to person.

Treatment does not remove the virus from the body. Antiviral medicines may help shorten the duration of a cold sore when used appropriately, particularly when treatment is started early. The virus remains in the body and can become active again in the future.

The stages of a cold sore

Recognising the sequence helps distinguish a cold sore from a bacterial sore, because impetigo does not follow this pattern.

Because the treatment window sits so early in that sequence, timing matters more than most people expect. Our guide on when to take aciclovir for a cold sore outbreak covers the

What Is Impetigo?

Impetigo is a common bacterial infection that affects the surface of the skin. It is not caused by the herpes virus, so it is different from a cold sore.

The bacteria can enter through broken or irritated skin, such as a cut, graze, insect bite, eczema, scabies or head lice. Impetigo can also develop on skin that has not been visibly damaged, so there is not always an obvious entry point. If bacteria infect the skin around an existing cold sore, this is known as secondary impetigo.

The two forms of impetigo

Non bullous impetigo is the most common type. It often starts as red sores or small blisters that burst and develop a golden or honey coloured crust. The sores commonly appear around the nose and mouth, although they can occur elsewhere. They may feel itchy and can sometimes be sore. Mild swelling or swollen lymph nodes near the affected area can also occur.

Bullous impetigo is less common. It causes larger, fluid filled blisters, usually on the arms, legs or body. These blisters can take longer to burst and may leave raw skin underneath. Some people with bullous impetigo may also have a fever, feel generally unwell or have swollen glands.

Symptoms can develop a few days after contact with the bacteria. Because impetigo spreads easily through close skin contact, it can pass between children and adults before the cause of the sores is recognised.

Treatment depends on how widespread the infection is and your clinical assessment. A healthcare professional may recommend an appropriate topical or oral antibiotic where needed. Good hand hygiene, avoiding scratching the affected area and not sharing towels or personal items can also help reduce the risk of spreading impetigo.

Impetigo vs Cold Sore: Side-by-Side Comparison

Is Impetigo Herpes?

No. Impetigo and cold sores are different infections caused by different types of germs. Impetigo is a bacterial skin infection, usually caused by Staphylococcus aureus or Streptococcus pyogenes. Cold sores are caused by herpes simplex virus type 1 (HSV 1).

It is easy to confuse the two because both can cause blisters or sores around the mouth, and both can be contagious. However, there are some useful differences.

Cold sores often start with tingling, itching or burning before small, fluid filled blisters appear. Impetigo can start as red sores or small blisters that break and develop a golden or honey coloured crust. Impetigo may also spread to nearby areas of skin, while a cold sore usually stays within the area affected by the outbreak.

Treatment is also different. Cold sores may be treated with antiviral medicines, particularly when treatment is started early. Impetigo may require a topical or oral antibiotic, depending on how widespread the infection is and what a healthcare professional recommends. Cold sore treatments will not treat a bacterial infection, and antibiotics do not treat the herpes simplex virus.

Good hygiene can help reduce the spread of both infections. Wash your hands regularly, avoid touching or scratching the sores, and do not share towels, lip products or other items that come into contact with the affected area.

If the sores are spreading, becoming more painful or swollen, producing pus, or you develop a fever or feel unwell, speak to a GP, pharmacist or other healthcare professional. An accurate diagnosis is important because the right treatment depends on the cause.

Can a Cold Sore Turn Into Impetigo?

Not exactly. A cold sore does not turn into impetigo because the two conditions are caused by different types of infection.

However, a cold sore can sometimes become secondarily infected with bacteria. When a cold sore breaks and weeps, it can leave the skin damaged. This gives bacteria an opportunity to enter the skin and cause impetigo. Cold sores are among the skin conditions that can sometimes be complicated by secondary impetigo.

This means that someone can have a cold sore and impetigo at the same time. The combination can be difficult to recognise because both conditions can cause crusting around the mouth. Impetigo may also spread beyond the area where the original cold sore appeared.

Signs a cold sore may have developed a bacterial infection

• The sores spread well beyond the original blister area.
• Golden or honey coloured crusting continues to spread.
• The surrounding skin becomes increasingly painful, swollen, warm or red.
• You notice pus or thick yellow discharge.
• The sore lasts much longer than you would normally expect.
• You develop a fever or feel generally unwell.

If you notice these changes, do not assume that an antiviral treatment alone will be enough. A healthcare professional can assess the area and decide whether treatment for a bacterial infection is needed.

There are also some simple steps you can take to reduce the risk of infection. Avoid picking or scratching the sore, wash your hands before and after touching the area, and do not squeeze the blisters. If you need to apply a cream, follow the product instructions and consider using a clean cotton bud rather than your fingertip.

Myths About Impetigo and Cold Sores

There are several common myths about impetigo and cold sores. Knowing what is true can help you avoid using the wrong treatment or spreading an infection to someone else.

Myth: Impetigo is a type of herpes

No. Impetigo is a bacterial skin infection, while cold sores are caused by the herpes simplex virus. They may look similar around the mouth, but they need different treatments. A cold sore treatment will not treat impetigo, while antibiotics do not treat the virus that causes cold sores.

Myth: Only children get impetigo

No. Impetigo is particularly common in children aged two to five, but adults can also develop it. The risk may be higher for people with conditions that cause broken or irritated skin, such as eczema, or for those who have close contact with someone who has impetigo.

Myth: Impetigo means poor hygiene

Not at all. Impetigo can affect anyone and does not mean that someone is unclean. The bacteria that cause impetigo can live on healthy skin without causing problems. If the skin becomes broken or irritated, the bacteria can sometimes enter and cause an infection.

Good hand hygiene can still help reduce the spread of impetigo, particularly in households, schools and other places where people are in close contact.

Myth: Cold sores are the same as genital herpes

They are caused by closely related herpes simplex viruses, but they are not exactly the same condition. HSV 1 is the most common cause of cold sores, while HSV 2 is more commonly linked with genital herpes. However, either type can affect the mouth or genital area.

Having a cold sore on your lip does not, by itself, mean that you have a sexually transmitted infection.

Myth: You can only pass on a cold sore when a blister is visible

Not always. The herpes simplex virus can sometimes be present on the skin even when there are no visible sores. This is known as asymptomatic shedding.

The risk of passing the virus on is generally higher when an active cold sore is present, but it is not completely absent between outbreaks.

Myth: A cold sore scab means you are no longer contagious

A cold sore becomes less likely to spread as it dries and heals, but it can still be infectious while it is healing. It is safest to avoid kissing and sharing items such as lip products, cups or towels until the sore has completely healed.

Myth: Antibiotics will clear a cold sore faster

No. Antibiotics treat bacterial infections and do not work against the herpes simplex virus. Using antibiotics when they are not needed can also contribute to antibiotic resistance.

An antibiotic may only be needed if a cold sore has also developed a separate bacterial infection. A healthcare professional can assess this and recommend appropriate treatment.

Cold Sore or Impetigo on the Lip?

Sores around the lips can be particularly difficult to identify because both cold sores and impetigo can blister, weep and develop crusts.

Some features may give you a useful clue, but they cannot confirm the diagnosis on their own.

Points that may suggest a cold sore

• You noticed tingling, itching or burning before the sore appeared.
• The blisters are small, grouped closely together and appear around the lip border.
• You have had similar sores in the same area before.
• The area feels tender, sore or painful.
• The outbreak stays within a relatively small area.

Points that may suggest impetigo

• The sores appeared without the usual tingling or burning warning.
• The sores develop a golden or honey coloured crust.
• The infection appears around the nose or chin as well as the mouth.
• New sores or patches appear in different areas of the body.
• The area is mainly itchy rather than painful.
• The person is a young child or has recently been in close contact with someone who has impetigo.
• There is a cut, graze, insect bite or another area of broken skin nearby.

These signs can help you understand what might be happening, but neither list can diagnose the infection by itself. If you are unsure, the sores are spreading or treatment does not seem to be helping, speak to a GP, pharmacist or other healthcare professional. This is particularly important for young children or when sores are affecting the face.

What Else Could It Be?

Not every sore around the mouth is a cold sore or impetigo. Several other skin conditions can look similar, including angular cheilitis, contact dermatitis, eczema and hand, foot and mouth disease.

The location, appearance, symptoms and how quickly the area changes can all help a healthcare professional work out the likely cause. If the diagnosis is unclear, an assessment is a safer option than trying several treatments yourself.

If sores are inside the mouth rather than on the outer lip, neither impetigo nor a typical cold sore outbreak is the most likely explanation. Mouth ulcers and other conditions can cause sores inside the mouth, so a clinical assessment may be appropriate, particularly if the sores are severe, keep coming back or do not heal.

Underlying Health Factors That Affect Skin Infection Risk

Some health conditions can make certain skin infections more likely or may make them slower to clear. This does not mean that the condition directly causes an infection.

Poorly controlled type 2 diabetes can affect the body's ability to fight bacterial infections and may slow wound healing. This means that a small cut or break in the skin may take longer to heal and may be more vulnerable to infection.

Higher body weight can also affect the skin in some people. Friction and moisture in skin folds can sometimes irritate the skin and make it easier for the skin barrier to break down. Higher body weight is also associated with an increased risk of type 2 diabetes.

This does not mean that impetigo or cold sores are caused by diabetes or body weight. The immediate treatment for the infection remains based on the diagnosis. However, if you are experiencing repeated skin infections and also have an ongoing health condition, it may be worth discussing this with your GP.

For readers whose wider health picture includes type 2 diabetes or weight management, Mounjaro and our weight loss treatments section provide information about available treatment options and eligibility. Suitability depends on an individual clinical assessment, and results vary between individuals.

How Each Condition Is Diagnosed

Both conditions can usually be diagnosed by a healthcare professional based on the appearance of the sores, your symptoms and where the affected skin is located. Tests are not always needed.

For impetigo, NICE guidance states that a skin swab is not routinely needed. A swab may be considered if the infection keeps coming back, has not responded to treatment or there is a concern about resistant bacteria. If impetigo repeatedly returns, a healthcare professional may also consider checking whether the bacteria are present in the nostrils.

Cold sores that return in a familiar pattern usually do not need testing. A viral swab may be considered if it is the first suspected outbreak, the symptoms are unusual or the diagnosis is uncertain. Testing may also be considered for people with a weakened immune system where confirming the diagnosis could affect treatment.

How Cold Sores Are Treated in the UK

Treatment for cold sores depends on the severity of the outbreak, your medical history and how often you experience them.

Antiviral medicines work by limiting the ability of the herpes simplex virus to multiply. They are generally most useful when started early, such as when you first notice tingling, itching or burning before the blisters appear. They may help shorten the outbreak for some people, but they do not remove the virus from the body.

Treatment options in the UK can include aciclovir tablets, aciclovir 5% cream for some localised outbreaks and valaciclovir, which the body converts into aciclovir. Valtrex is a branded form of valaciclovir.

The most suitable treatment, strength and duration depend on your symptoms and medical history. If you have frequent, severe or unusually persistent cold sores, speak to a GP or pharmacist about whether prescription treatment is appropriate for you.

Cold sore treatment pricing

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How Impetigo Is Treated in the UK

Impetigo treatment follows NICE guideline NG153 on antimicrobial prescribing. Because impetigo is a bacterial infection, antiviral treatment used for cold sores will not treat it.

For localised non bullous impetigo in someone who is otherwise well, a healthcare professional may recommend hydrogen peroxide 1% cream as a first option. If this is not suitable, such as when the infection is close to the eyes, or if it has not helped, a short course of a topical antibiotic such as fusidic acid may be considered.

More widespread non bullous impetigo may need a topical or oral antibiotic, depending on the individual situation. Bullous impetigo, or impetigo in someone who feels generally unwell or has a higher risk of complications, may require an oral antibiotic.

NICE advises against using topical and oral antibiotics together for impetigo unless there is a specific clinical reason. Treatment is often given for around five days, although the exact treatment and duration depend on the assessment.

In England, eligible people may be able to use the Pharmacy First service for impetigo. A participating community pharmacist can assess the infection and, where appropriate, provide treatment without the need for a GP appointment.

Contagiousness, School and Work

Impetigo and cold sores are both contagious, but the advice about returning to school or work is different.

For impetigo, NHS guidance generally recommends staying away from school, nursery, work or playgroup until the sores have dried and crusted over, or until 48 hours after starting treatment, depending on the circumstances.

Avoid sharing towels, flannels, clothing or bedding with someone who has impetigo. Washing these items regularly can also help reduce the risk of spreading the infection.

Cold sores are most easily spread when the blisters are present and weeping. They can spread through direct contact, including kissing, or by sharing items such as cups, cutlery, lip balm or towels. There is no general requirement to stay away from school or work because of a cold sore, but direct contact with the sore should be avoided.

Reducing spread within a household

• Do not share towels, flannels, bedding, razors or lip products.
• Wash clothing and linen regularly, following the highest safe temperature stated on the care label.
• Keep fingernails short, particularly for children with impetigo, to reduce scratching.
• Cover impetigo sores loosely where practical and try to prevent scratching.
• Wash your hands thoroughly after touching sores or applying cream.
• Avoid activities involving close skin contact, such as contact sports, until the infection has healed.

One important precaution applies particularly to cold sores: avoid contact with newborn babies. Neonatal herpes is rare but can be very serious. If you have an active cold sore, do not kiss a newborn baby.

If you are pregnant or breastfeeding and are unsure whether a particular antiviral or other treatment is suitable, speak to your midwife, GP or pharmacist before using it.

Possible Complications

Most cases of impetigo and cold sores clear without serious problems, but complications can sometimes occur.

Impetigo can occasionally spread deeper into the skin and cause cellulitis. This can cause spreading redness, warmth, swelling and tenderness around the affected area. Less common complications can include scarlet fever, guttate psoriasis and, rarely, kidney inflammation following certain streptococcal infections. Scarring is uncommon.

Cold sores can sometimes spread to the eye. A herpes infection affecting the eye, known as herpetic keratitis, can affect vision and needs prompt medical assessment.

People with eczema can rarely develop eczema herpeticum, where the herpes virus causes a rapidly spreading and painful rash. This can be serious and requires urgent medical attention. People with a weakened immune system may also experience more severe or longer lasting outbreaks.

When to Seek Medical Advice

Speak to a healthcare professional if:

• The sores are spreading quickly or new areas are becoming affected.
• Impetigo has not improved after treatment.
• A cold sore has not started to heal after around 10 days.
• You develop a fever or feel generally unwell.
• The affected person is a newborn.
• You are pregnant and are unsure about suitable treatment.
• You have a weakened immune system.

Seek same day medical advice if the skin around the sores becomes increasingly red, warm, swollen or painful, as this may be a sign of cellulitis. You should also seek prompt medical advice if sores are close to or affecting the eye, or if someone with eczema develops a rapidly spreading and painful rash.

In these situations, contact your GP or NHS 111 for advice.

Medical Disclaimer

This article covers two separate conditions, only one of which is treated through this service. Information about impetigo is provided to help readers understand when their symptoms may not be a typical cold sore and when they may need professional advice. It is based on NICE guideline NG153 and NHS guidance, but it does not replace an assessment by a pharmacist, GP or other qualified healthcare professional.

Do not use this information to self diagnose a skin infection, particularly if the affected person is a child, newborn, pregnant or has a weakened immune system. The other conditions mentioned in this article are included to show why professional assessment may sometimes be needed.

References to conditions such as type 2 diabetes and weight management are provided as general health information only. They do not mean that weight management or diabetes treatment can prevent, treat or shorten a skin infection.

Prescription treatment is only supplied after an assessment by a UK registered prescriber, who will decide whether treatment is suitable for you. Results vary between individuals.

If sores are spreading, getting worse, accompanied by a fever, or affecting the area around the eye, seek medical advice promptly rather than relying on information found online.