Hydrogen Peroxide & Cold Sores


Cold sores generally appear on the outside of the mouth but they can also appear in the soft tissues of the mouth. They are caused by the herpes simplex virus. Hydrogen peroxide is just one type of home remedy that may be used to improve the symptoms associated with the cold sore. Individuals should consult a health care professional before using hydrogen peroxide for a cold sore.


The herpes simplex virus, or HSV, infects different parts of the body. The most common locations are the lips, cheeks, nose and sometimes in the eye. Once an individual contracts HSV, the virus remains in his body for life. When the virus is activated, it produces blisters, called cold sores when they appear near the mouth. Some individuals may have frequent flare ups, one initial flare up followed by no activity, or no sign of infection at all. HSV can spread from one person to another despite a lack of cold sores.

Symptoms of Cold Sores

Cold sores can be very painful and unsightly. The skin infected with HSV will present prodrome, or warning symptoms before a cold sore actually appears. This prodrome phase is not always present or recognized. It consists of tingling, redness, itching and tenderness. Between a few hours and one day after prodrome symptoms appear, the individual will notice fluid-filled blisters on the skin. These may be cloudy or appear to be filled with pus. They can be confused with pimples or bug bites. The sores will burst, ooze fluid and sometimes blood and finally scab over. The scabs may fall off and reappear before the skin fully heals. While this is occurring, new blisters can appear and the individual is contagious, meaning the HSV can be spread to another person who comes in contact with the fluids.

Home Treatment

Home treatment typically consists of methods that reduce pain and help to dry the cold sores to speed healing. Hydrogen peroxide can be used as a cleansing antiseptic to prevent infection of the sores and to promote healing, suggests the University of Iowa Hospitals and Clinics. To use hydrogen peroxide on cold sores, it should be mixed with an equal amount of water. The solution can be swished around the mouth if this is where cold sores are located, or it can be applied to the sores on the outside of the face using a cotton swab.


The peroxide may cause bubbling and some pain or tingling when applied. The solution should not be applied or swished so vigorously that it dislodges a scab. Instead, the peroxide should be used during the blister phase up until the early scab phase. The soft scab that still seems wet should not be treated with peroxide, as this can only prolong the existence of the sore.


Hydrogen peroxide will not prevent new blisters nor will it make an individual any less contagious. The solution should only be used under the recommendation of a health care professional. Other methods of home treatment may be more effective or preferred, such as applying ice packs or mixing baking soda or salt with water to form a paste. The paste can be applied to the skin to help to dry the sore.

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