Does Hydrogen Peroxide Work On Cold Sores?

An open blister is susceptible to bacterial infection and other foreign organisms, potentially resulting in dangerous or fatal medical conditions if left unattended. Hydrogen peroxide¹ is a potent antiseptic used to treat cold sores and may also treat minor burns, scrapes, and cuts, making it an excellent treatment option for most cold sore victims. It kills bacteria by drying out and sterilizing the area.

Hydrogen peroxide can help with sores, cuts, and other dermatological applications when used in appropriate amounts. However, we encourage you to consult your healthcare provider to determine whether you can use hydrogen peroxide for your cold sores without suffering any side effects.

This guide will help you understand the etiology of cold sores and the effectiveness of hydrogen peroxide on cold sores as a treatment agent.

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Popping a cold sore is very tempting. However, doing so exposes the skin and releases infectious fluids that increase the risk of spreading the infection and causing scarring.

What is a cold sore?

A cold sore is a small, fluid-filled blister that forms around the lips and cheeks and on the skin around the genitals. Medical journals also refer to cold sores as oral herpes or fever blisters. When the surface of one of these blisters breaks, a scab forms that may take weeks to heal without leaving a scar. They affect the skin after a herpes simplex virus (HSV)² infection.

The World Health Organization states that children are at a higher risk of contracting HSV than adults. The virus is highly contagious. You may contract it through sharing drinks and food or kissing. Once the virus enters the body, it hibernates but can cause recurring cold sores.

What are the causes and symptoms of cold sores?

As aforementioned, cold sores mainly occur after herpes simplex virus type 1 (HSV-1) infection. However, there are fewer common cases of cold sores caused by HSV-2.     

Cold sores have no actual cure. Once you have contracted the virus, it stays in your body.

However, the sores usually heal by themselves in 1–2 weeks. Medical practitioners may recommend antiviral creams and pills to manage outbreaks.

Effective treatment decreases the severity, length, and frequency of future outbreaks.

Cold sores are highly contagious, especially when the damaged skin is oozing bodily fluids. Many people with HSV-1 never show visible signs and symptoms. But cold sores can appear in reaction to specific triggers, including the following:

  • Hormonal changes

  • Stress

  • Wind and dry weather

  • Sun or wind exposure

  • Injury to the skin

  • Fatigue

  • Fever or viral infection

  • Immune system changes

HSV is highly contagious and transmits via oral contact, including oral sex, sharing drinks and food, and kissing. Symptoms will also include:

  • Swollen lymph nodes

  • Muscle aches

  • Headache

  • Sore throat

  • Painful gums

  • Fever

Children under five may get cold sores in their mouths, which people can mistake for canker sores. The latter is not caused by the herpes simplex virus that attacks the mucous membrane.

How common is it?

50-80%³ of the American adult population has HSV. The National Library of Medicine cites that approximately 90%⁴ of adults are exposed to the infection by the time they are 50 years old.

After infection, the individual will have HSV for the rest of their life as the virus remains dormant in the patient's body. Some people may never show symptoms, while others will have recurring infections.

What are the risk factors?

Most adults carry the virus even if they have never experienced any symptoms. Almost everyone is at risk of infection. You may be at an increased risk if you have a compromised immune system from treatments and conditions such as:

  • Anti-rejection medications for organ transplants

  • Cancer chemotherapy

  • Atopic dermatitis (eczema)


Consult your medical practitioner if you develop complications affecting other areas of your body, including large sections of the skin, eyes, and fingertips.

What are the stages of cold sores?

A cold sore evolves through multiple phases:

  • Itching and tingling. Most patients experience a tingling, burning, or itching sensation around the lips before blisters erupt and a small, painful, hard spot emerges.

  • Blisters. These are tiny fluid-filled sacs that erupt along your lip's borders. Sometimes, they appear inside the mouth, cheeks, or nose.

  • Oozing and crusting. The tiny blisters may burst, leaving superficial open sores that ooze and crust over.

Cold sore signs and symptoms vary depending on whether it is a first-time infection or a recurrence. You will notice early symptoms within the first 20 days of initial virus exposure. The sores may last several days, while blisters take approximately three weeks to clear. 

Recurrences will also be less aggressive and appear around the same spot.

Is hydrogen peroxide a cure for cold sores?

We recommend consulting your healthcare physician before applying hydrogen peroxide on cold sores. Like with other treatments, people react differently to hydrogen peroxide. Your healthcare provider will help you decide whether hydrogen peroxide is suitable for curing your cold sores.

Hydrogen peroxide may help to heal cold sores as it has antiviral and antibacterial properties.

Using hydrogen peroxide to cure cold sores

This segment provides a comprehensive overview of using hydrogen peroxide for cold sores.

How does it work?

Hydrogen peroxide's antibacterial and antiviral properties counteract HSV symptoms and further infection when diluted appropriately. However, it may not be the best option for alleviating severe cases that require further medical attention.

Hydrogen peroxide contains several bacteria-fighting and healing properties that decrease the cold sore's healing time and prevent blisters from spreading. It dehydrates cold sores and reduces inflammation.

While subjective, this chemical compound could help to eliminate the sores in a few weeks when applied appropriately. Speak with your doctor before using hydrogen peroxide on your cold sore.

How to use hydrogen peroxide for cold sores

Here's a detailed breakdown of how to use hydrogen peroxide on cold sores:

  • Pour one tablespoon of 3% hydrogen peroxide into a bowl.

  • Place tissue or cotton ball into the liquid.

  • Identify the location of the cold sore and gently position the saturated material on the skin. Don't apply intense pressure or rub the area.

  • Maintain this technique for about ten minutes or less. Rinse the skin with clean water.

  • Repeat this procedure 3–4 times per day for the best outcomes.

You could burn your skin if it is sensitive or dry. Ensure you use 3% hydrogen peroxide and dilute it with water before application. A peroxide solution with a higher percentage than the one recommended could cause severe damage to the skin.

How often should you use this?

Repeat the procedure above once or twice per day. Again, we recommend talking to your healthcare physician before using hydrogen peroxide to treat your cold sores.

Why does it work?

Hydrogen peroxide has antiviral and antibacterial properties that kill bacteria. It cleanses your skin and kills microorganisms that may encourage cold sores. Its antiviral properties target HSV, which causes cold sores by weakening the virus's molecular framework.

Hydrogen peroxide also helps lighten the blister scars that cold sores may leave behind. Its skin-bleaching properties make it a great option when applied appropriately.

Other treatment methods for cold sores

If you're on a budget and need an alternative to hydrogen peroxide for cold sores, consider the following recommendations:

Salt and hydrogen peroxide for cold sores

For this treatment, you'll need a 3% hydrogen peroxide solution and one teaspoon of salt. Create a paste by combining hydrogen peroxide and salt. Apply the paste to the affected area and allow it to dry, then rinse with clean water.

Apply the mixture twice a day for the best results. This method works because salt possesses antimicrobial properties and can speed up the healing time of cold sores, particularly when combined with hydrogen peroxide. Remember to check with your doctor before starting any new treatment.

Does toothpaste or hydrogen peroxide help?

Toothpaste is one potential alternative remedy for cold sores. Applying it to the cold sores during the blister phase keeps them from growing larger, dries them out, and makes the area numb. Most toothpaste manufacturers use sodium lauryl sulfate (SLS) as an active compound, which could prevent cold sore blisters.

For this treatment, apply a thin layer of non-gel, white SLS toothpaste to the area before bed and every two hours the following day. Gently remove the toothpaste with a sterile cotton ball dipped in warm water. This technique is as effective as hydrogen peroxide in drying out the blisters. Discuss this with your physician before starting treatment.


Your healthcare provider may prescribe antiviral drugs to manage HSV if you develop cold sores multiple times per year or are at a higher risk of developing further complications. Consider applying sunscreen if sunlight triggers frequent recurrences, and use sunblock on the sections where the sores erupt.

To reduce the probability of spreading cold sores to other people or other parts of your body, consider some of the precautions below:

  • Maintain clean hands. Wash your hands frequently if you have cold sores, and be careful when touching yourself or other people.

  • Avoid sharing items. Refrain from sharing lip balm, towels, utensils, and other personal items that can spread the infection, particularly when you have blisters.

  • Avoid skin contact and kissing. The virus primarily spreads when the blisters leak fluid.

You should also consult your doctor on whether an oral antiviral drug is a viable preventative option, especially if you need to perform activities that may trigger an outbreak, such as exposure to intense sunlight.

The lowdown

While hydrogen peroxide can be an effective treatment compound for cold sores, consult your physician before using it. The pure formulas available at the drugstore are not medically proven as effective agents for skin conditions and concerns.

Talk to your healthcare provider about professional procedures and over-the-counter (OTC) products that you intend to use on cold sores. Use hydrogen peroxide sparingly to maximize potential benefits to the cold sore. The more you maintain hygiene, the faster the wound will dry up without spreading. Consider hydrogen peroxide as a home agent to treat cold sores.

  1. Hydrogen peroxide | NIH: National Library of Medicine

  2. Herpes simplex virus | World Health Organization

  3. Oral herpes | Johns Hopkins Medicine

  4. Chapter 36 persistence in the population: Epidemiology, transmission (2007)

Other sources:

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