Impetigo vs. Cold Sore: What Are the Differences?

Impetigo and cold sores are common skin conditions that can lead to uncomfortable or painful sores or blisters, usually around the mouth. Bacterial infection causes impetigo, while viral infection causes cold sores.

Though both of these conditions may show up as blisters around the mouth, there is usually a telltale sign that helps differentiate one from another. A healthcare provider can usually diagnose a cold sore versus impetigo by looking at the affected area of the skin. Impetigo and cold sores can spread to others but are also preventable. 

This article discusses the similarities and differences between impetigo and cold sores, including symptoms, causes, and treatment. If you think you or a family member may have a cold sore or impetigo, see a healthcare provider so you can get the right diagnosis and treatment.

Symptoms

Cold sores are small blisters that often occur in clusters around the mouth or sometimes inside the mouth. Cold sores crust over and form scabs before they go away. Some people may not have symptoms the first time they have an outbreak, and some may never have symptoms even though they carry the virus that causes cold sores. 

Symptoms of cold sores can differ from person to person, but the most common symptoms are:

• Tingling lips
• Sore lips and mouth
• Small blisters on the mouth and lips that increase in size then burst and crust over
• Dry, itchy, irritated mouth

Symptoms of impetigo include red, itchy sores that occur on the skin, usually in exposed areas such as around the mouth and nose or on the arms and legs. In young children, it may occur around the diaper area. There are three types of impetigo:

• Nonbullous: Small blisters that burst and crust over
• Bullous: Large blisters that last longer without bursting
• Ecthyma: Ulcers with yellow crust and red edges

Nonbullous impetigo is the most common type. It usually occurs when skin has been damaged or irritated. The sores leak clear fluid for a few days, then crust over into yellowish scabs while the skin heals. The honey-colored crust that forms over the sores is a telltale sign of this form of impetigo.

Causes

Though both impetigo and cold sores show up as sores, the underlying causes of each are different. One of two types of bacterial infection causes impetigo, whereas a viral infection causes cold sores.

Causes of Impetigo

Two types of bacterial infections cause impetigo: group A Streptococcus and Staphylococcus aureus. When the bacteria get into the skin, they cause sores. Someone can get impetigo if their skin comes in contact with the sores or the fluid from the sores of someone with impetigo.

Anyone can get impetigo, but children are more at risk. It is most common in children 2–5 years old. Day cares and schools are common places where children may get impetigo due to many kids coming into close contact with one another.

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Causes of Cold Sores

Herpes simplex virus type 1 (HSV-1) is a common cause of cold sores. This is different from herpes simplex virus type 2 (HSV-2), a common cause of genital herpes, but either virus can cause oral or genital sores.

Sharing things that would have come in contact with someone’s cold sore, such as utensils or towels, can transmit HSV-1. It can also spread when kissing someone with a cold sore. Many people with cold sores have gotten HSV-1 as young children.

When someone has the virus, an outbreak of cold sores can be triggered by:

• Sun exposure
• Cold wind
• Having a cold or another type of illness
• A weakened immune system
• Stress

Diagnosis

A healthcare provider can examine the sores and diagnose impetigo or cold sores. Sometimes they may need to take a sample of the sore or the fluid from the blisters to be sure of the diagnosis.

Treatment

Treatment for impetigo and cold sores differs, so getting a correct diagnosis is key to making symptoms go away.

Impetigo Treatment

Because a bacterial infection causes impetigo, antibiotics are the go-to treatment to get rid of the bacteria. If the affected area of the skin is small, a healthcare provider may prescribe an antibiotic ointment to treat the infection.

If the infection has spread to other parts of the body or if the ointment doesn’t work, an antibiotic pill or liquid is usually prescribed. 

Cold Sore Treatment

There is no cure for the virus that causes cold sores, but there are treatments that can make cold sores more tolerable and go away more quickly. Some common treatments for cold sores include:

• Prescription or over-the-counter ointments
• Eating cold food or drinks to make eating more comfortable
• Putting something cool on the sores, such as a cold compress
• Tylenol (acetaminophen) or Advil or Motrin (ibuprofen) to help with pain

Prevention

Though both cold sores and impetigo are common, they are preventable. Because cold sores and impetigo are contagious, knowing how to prevent them can help keep them from spreading to others.

Impetigo Prevention

Because bacterial infection causes impetigo, keeping skin clean is key to prevention. This is especially important for broken skin, such as from a scrape or cut, and irritated skin due to rashes.

Covering affected areas with gauze and tape can help prevent impetigo from spreading to others. If someone is infected within a family, ensuring that the person with impetigo does not share things that would come into contact with their skin, such as towels, clothing, and bedsheets, helps prevent it from spreading to other family members.

Cold Sore Prevention

People who have never had cold sores can prevent them by avoiding skin-to-skin contact with someone who has an active cold sore.

For someone with a history of cold sores, future outbreaks can be prevented by avoiding the triggers that cause outbreaks. For example, if sun exposure is a trigger, wearing skin-protective clothing and sunscreen may help keep a cold sore outbreak at bay.

Another trigger may be stress. Though you may not be able to prevent the stressful situation, knowing that cold sores often happen when you are stressed is helpful to know because you can then prepare for them with treatments when they do show up.

Summary

Both impetigo and cold sores are common skin conditions that cause blisters to form, usually around the mouth. Though the blisters may look similar in some cases, the causes of these skin conditions are different, and there are telltale signs and symptoms that help differentiate the two.

A healthcare provider’s diagnosis is important for learning what treatments are available. Preventing cold sores and impetigo is possible, and though there is no cure for the virus that causes them, treatments can help keep them from recurring and make them go away faster.