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Cold Sores - Causes, Symptoms, Risk Factors, Diagnosis, and Treatment

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Infection around the border of the lips due to the herpes simplex virus is known as cold sores. To know about it in detail, read the article below.

Medically reviewed by

Dr. N. Ashok Viswanath

Published At March 11, 2022
Reviewed AtDecember 27, 2023

What Are Cold Sores?

Cold sores are most commonly referred to as fever blisters or tiny blisters caused by a viral infection. They are typically small in size and filled with fluids that occur on and around the lip region. In most cases, these blisters tend to group together and produce a patch-like appearance. These cold sores can spread from one affected person to another through close contact, like kissing.

These cold sores last only for two or three weeks and leave without causing any scars or marks. When the fluid-filled blisters break, scab forms, and it lasts for at least three to four days before falling off. Even when the sores are not visible, the cold sores tend to spread. It can also spread to another person’s mouth or genitalia when involved in oral sex.

Causes of cold sores

What Are the Causes of Cold Sores?

As mentioned earlier, cold sores are caused due to viral infection. The main virus that is responsible for causing cold sores is a certain strain of the herpes simplex virus (HSV). To be more descriptive, HSV-1 causes cold sores, whereas HSV-2 is responsible for genital herpes. But both these have the danger of spreading to another person’s mouth or genitalia through close contact and oral sex.

Cold sores are most contagious when the fluids from the blisters are oozing out since these fluids are easy to spread through contact. But it is also possible for the virus to get transmitted even if there are no blisters. It has been observed that many cases of cold sores have not exhibited any signs or symptoms.

There is a possibility of the herpes virus being present dormant in the nerve cells after an episode of the infection. This means that there are chances of getting another cold sore exactly at the same spot as before. These recurrences might be triggered by the following factors.

  1. Stress.

  2. Fever or viral infection.

  3. Hormonal changes.

  4. Fatigue.

  5. Sunlight exposure.

  6. Injury to the skin.

  7. Change in immunity.

What Are the Symptoms of Cold Sores?

The signs and symptoms of cold sores may vary depending on whether the person is getting the sores for the first time or if it is a recurrence. There are three different phases throughout the lifetime of the cold sore. They are:

Itching and Tingling: Upon getting the infection, many would experience itching, tingling, or burning sensation on and around the lips. During this time, there will be no signs of blisters or pain.

Blisters: After a day or two of the irritation, small, hard, and fluid-filled blisters begin to erupt along the borders of the lip. There is a possibility of these blisters showing up on the cheeks and around the nose.

Oozing and Crusting: These blisters might start to combine and form patches that eventually burst and ooze out fluids. This leads to the formation of scabs, and then the healing process begins.

The signs do not appear for the first time and until after 20 days of initial exposure to the virus. Recurrence usually occurs at the same spot and is comparatively less severe than the first infection. Some of the common symptoms for a first-time outbreak include:

  • Sore throat.

  • Headache.

  • Fever.

  • Muscle aches.

  • Painful gums.

  • Swollen lymph nodes.

What Are the Risk Factors of Cold Sores?

There is no specific group of populations that is more susceptible to cold sores. In fact, almost every person has the risk of getting a cold sore. Though there are no symptoms, almost all adults serve as a carrier for carrying the virus that causes cold sores.

One main factor that plays a vital role in the development of cold sores is due to a weakened immune system. It can be due to other medical conditions or treatments such as:

  • Eczema.

  • HIV or AIDS.

  • Anti-rejection drugs which are used for organ transplants.

  • Chemotherapy for cancer.

How Are Cold Sores Diagnosed?

Cold sores are very easily diagnosed. The doctor will have a look at the blisters and directly confirm cold sores. If in case there is a need to confirm the diagnosis, a sample might be taken from the blisters, which is sent to the laboratory for testing. Apart from these, there are no other methods required for diagnosing cold sores.

How Are Cold Sores Treated?

Cold sores are often left untreated, and it goes away on their own in two weeks to four weeks. If the doctor feels the requirement of any antiviral medications in order to speed up the healing process, then there are different prescription medicines that are available. They are:

  • Famciclovir.

  • Acyclovir.

  • Penciclovir.

  • Valacyclovir.

These medicines are available in different forms as well. For instance, some of these medicines are available in the form of pills that can be taken orally, and others are available in the form of creams, which can be applied over the blisters or the sores as per the doctor’s direction. Usually, the doctor will advise applying the creams two to three times a day.

In terms of efficiency, it has been said that the pills work better than the creams. In cases of utmost severe infections, antiviral drugs are given in the form of an injection to help fight the infection.

How to Prevent Cold Sores?

The main concept behind the prevention of cold sores is to maintain personal hygiene and avoid all the things that trigger cold sores. If the sores are caused due to sun exposure, proper sunblock or oral antiviral drugs (prescribed by the doctor) help to prevent them. Also, if a person is getting cold sores more than nine times a year, then the doctor will prescribe an antiviral medication which is to be taken on a regular basis to avoid any further recurrence.

Avoid the following in order to prevent yourself from catching the infection from other persons.

  • Always keep your hands clean.

  • Avoid skin contact and kissing people who have blisters.

  • Avoid sharing utensils and towels.


Cold sores are not a severe health condition; generally, it goes away on their own without any medical intervention. The treatment focuses on managing the outbreak and speeding up the healing process. If the recurrence is very frequent, reach out to your doctor to get antiviral medications that can be helpful in reducing the intensity and the frequency of the outbreaks.

Frequently Asked Questions


How to Relieve Cold Sores Fast?

A cool, damp cloth can help reduce redness, remove crusting, and promote healing. To relieve pain, apply a warm compress to the blisters. Rest and pain relievers are recommended. Take over-the-counter pain relievers if one has a fever, or the cold sore is painful.


Are All Cold Sore Viruses STDs?

A cold sore does not always imply the presence of an STD. Herpes simplex type 1 (HSV-1) causes most cold sores, which typically affect the lips and are not transmitted through sexual contact. However, cold sores can be caused by another herpes simplex virus called HSV-2, which is less common. This virus is commonly responsible for herpes genitalis, a genital STD.  HSV-1 and HSV-2 can be transmitted through body secretions, saliva, or oral sex. 


Are Cold Sores Serious?

Cold sores are not generally dangerous and do not cause permanent skin damage. However, treatment does not heal the infection and is not required in most cases. Most people get the cold sore virus as a child from an adult who has the virus.


What Are the Stages of Developing Cold Sores?

- Cold Sore Stage 1: Initial symptoms include tingling, soreness, tightness, or itching around the lips (days one to two).
- Cold Sore Stage 2: Formation of red, fluid-filled blisters (days two to four) as the virus multiplies and the body fights back.
- Cold Sore Stage 3: Blisters burst open and become painful ulcerated sores that scab over (days four to five).
- Cold Sore Stage 4: Scab formation (days five to eight), which can be itchy, crack, and bleed.
- Cold Sore Stage 5: Scabs fall off, and skin may appear pink or reddish (days eight to ten).


Can Cold Sores Spread Through Kissing?

Yes, kissing can cause oral herpes, also known as cold sores, though developing genital herpes is less likely. Oral herpes (HSV-1) is typically transmitted through kissing, whereas genital herpes (HSV-2) is typically transmitted through vaginal, anal, or oral sex.


How to Prevent Cold Sores Naturally?

Cold sores thrive when the immune system weakens, so eating foods that boost immunity is a tried-and-true way to keep them at bay. Consume plenty of fresh fruits and vegetables (especially those high in vitamin C) and probiotic foods such as yogurt, kimchi, and sauerkraut.


Do Cold Sores Affect Everyone?

Cold sores can affect almost anyone. Even if they have never had cold sores, most adults carry the virus that causes them. In addition, if one has a weakened immune system due to conditions or treatments such as HIV (human immunodeficiency virus) or AIDS (acquired immunodeficiency syndrome), they are more likely to develop complications from the virus.


When Are Cold Sores Most Contagious?

Cold sores are often highly contagious from the moment they appear. It usually takes one to two days before the sore becomes visible. The virus can be transmitted for up to 15 days. People should be cautious not to spread the virus during an outbreak.


Can Vaseline Help With Cold Sores?

A petroleum jelly like Vaseline will not necessarily heal a cold sore but may provide temporary relief. The jelly prevents cracking. It also acts as a barrier against external irritants. Although witch hazel is a natural astringent that helps dry out and heal cold sores, it can sting when applied.


Can Ice Cubes Heal Cold Sores?

Ice may provide temporary relief from the symptoms and aid in reducing redness and swelling. Applying ice for five to ten minutes every hour during the tingle phase helps numb the area and slows the development of the sore by decreasing blood flow. However, it does not hasten the healing of the cold sore.


Is It Safe to Apply Toothpaste to Cold Sores?

According to the wound care society, applying toothpaste to cold sores during their blister phase may numb the area, dry the blisters, and prevent them from spreading. Most toothpaste contains sodium lauryl sulfate (SLS), which is thought to prevent cold sore blisters. Unfortunately, the only evidence that toothpaste is effective for cold sore prevention or treatment is anecdotal.


How Prevalent Are Cold Sores?

Because the virus that causes cold sores is highly contagious, cold sores affect many people. This virus usually infects children. A child often contracts the virus after being kissed by someone with a cold sore. Even if they have never had cold sores, most adults carry the virus that causes them.


Are Cold Sores Inherited?

Cold sores are not inherited in the traditional sense. Cold sores are not a genetic disorder. However, genes appear to be linked to whether or not you get cold sores after contracting Herpes simplex. Most HSV infections in newborns are caused by HSV-2, which the infant picks up from the mother's birth canal. HSV-1 can be transmitted to newborns through close contact with someone shedding the HSV-1 virus in their saliva or having an active HSV-1 outbreak (cold sores).


How Many Cold Sores Are Normal in a Year?

Cold sores typically reappear three to four times a year, though some people may get more than one per month. In general, the frequency and severity of outbreaks decrease over time. Before an outbreak, people frequently experience tingling, burning, or itching at the site.
Dr. N. Ashok Viswanath
Dr. N. Ashok Viswanath

Infectious Diseases


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