Cold Sores - Symptoms, Causes, and Treatment

Dr. Pradeep Vangala | July 17, 2020

What are cold sores?

Cold sores, also known as fever blisters, are red, fluid-filled, painful blisters caused by herpes simplex virus (HSV). They are generally grouped in patches and appear around the lips. Rarely they appear on the nose, fingers, or inside the mouth. Cold sores heal within two to three weeks without leaving any scar. Cold sores are a contagious infection and can spread through close contacts, such as kissing. These cold sores can spread even when they are not visible. There is no permanent cure for cold sores, and they keep returning without any warning. Treatment and medications can help you to manage these outbreaks and reduce their recurrence.



Cold sores lead to the formation of painful blisters, typically only on one side of the lips. Then the blisters spread to the surrounding skin or into the mouth. The blisters can break open when you talk, laugh, or chew, oozing out the liquid. Foods that are acidic and some drinks like citric juice or vinegar can irritate the lesion. When these wounds heal, it crusts. Cold sores are usually more unpleasant the first time you get them because your body doesn’t yet have any antibodies to fight against the virus. You may experience symptoms such as fever, weakness, and enlarged lymph nodes in the neck area. Young children may experience fever during their first episode of a cold sore. Your mouth may become severely inflamed and painful. This leads to bad breath.

Once you are exposed to the herpes virus infection, it takes 15 to 20 days for the symptoms to appear. The symptoms of cold sore pass through various stages.

  • Itching, tingling, or burning sensation around the lip.
  • Blister appears after a day, which becomes red, swollen, and painful.
  • Blisters break open into shallow sores.
  • A crust forms over the sore, which might break and bleed.
  • Then the coat falls off.

Consult your doctor if:

  • There is high fever and chills.
  • The sores are excruciating and need medication.
  • Cold sores are spreading to other areas of your body.
  • You have recurrent cold sores.
  • The cold sores don’t heal within two weeks.

Causes of Cold Sores

Cold sores result from HSV or herpes simplex virus infection. It includes two types of herpes simplex viruses, type 1 and type 2. Cold sores are the outcome of herpes simplex type 1, but sometimes it can be due to herpes simplex type 2, which can cause genital herpes. This infection spread through the fluid in the blisters or open sores, for instance, through kissing, oral sex, or shared objects. Some studies say that cold sores may occur if the immune system is weak, for instance, due to a common cold or after exhausting physical activity. But it is not clear why some people get recurrent cold sores (1). Some people do not develop any signs or symptoms of cold sores but can still spread the virus. Once you have a herpes infection, the virus remains in your nerve cells under your skin and can reoccur in the same place. Few factors like fever, stress, fatigue, sunlight, and reduced immunity can trigger the outbreak of cold sores. Oral sex can result in both cold sores and genital herpes.

Risk Factors

Risk factors of cold sores are linked to conditions causing a weakened immune system.  Few health conditions or treatments that pose a potential risk are;

  • Stress
  • Menstruation
  • Exposure to sun
  • Cancer Chemotherapy
  • Medications used for organ transplants
  • Atopic dermatitis or eczema


Complications are rarely seen in cold sores, but in younger children, it becomes a cause of concern.

Look for immediate medical attention if you experience following symptoms;

  • Persistent high fever
  • Irritation or redness of eyes
  • Difficulty in breathing or swallowing

Cold sores sometimes cause an eye infection, which may lead to vision problems. In people who have skin problems like dermatitis, it may spread to other parts resulting in a medical emergency. Consult a doctor in initial stages to avoid such complications.


If you are experiencing recurrent cold sores, your doctor may advise you on some antiviral medications. If there is any triggering factor like sunlight or skin problems, the doctor can advise you on some preventive measures to be followed. Discussing with your doctor can help you to understand the preventive measures you need to take to avoid cold sores.

Some tips to prevent cold sores;

  • Avoid kissing or any skin contact with people who have blisters. The virus spreads mostly through the blisters that leak fluid.
  • Avoid sharing items like utensils, towels, lip balm, and other personal things that can spread the virus when blisters are present.
  • Always keep your hands clean. Wash your hands carefully before touching yourself, others, and younger kids.
  • Apply sunscreen before prolonged sun exposure.

Treatment for Cold Sores

There is no permanent remedy for cold sores, but prompt topical treatment and oral medications can reduce its severity and duration. There are several treatment approaches for cold sores.

Antiviral Creams and Ointments

Cold sores generally clean up on their own. Antiviral ointments, creams, patches, or gels can speed up the healing process, and they can also prevent blisters and scabs from forming. In order for these ointments to work, it should be applied within 24 hours of the first symptoms arising. These antiviral creams should be applied to the affected area every 2 to 3 hours, for five days.


Cold sores are treated with antiviral drugs such as oral acyclovir. These drugs are available on a prescription base only. Your doctor may recommend you to take antiviral medication on a regular basis to prevent outbreaks and complications. You may experience a few minor side effects like headache and nausea with these medications. 500 mg to 1 g Valacyclovir oral tablet is advised twice a day. Medication should be started as soon as the first symptom appears. This oral tablet is available under the brand name Valtrex. Dosage and duration vary depending on the severity of cold sores and your health condition. Valacyclovir is associated with various adverse effects such as allergic reaction, harmful effects on the kidney and nervous system, hence doctors’ consultation is required before taking these drugs.

Some Home Remedies to Ease Cold Sores

  • You can try some remedies at home to soothe cold sores, such as applying a cold compress. Using a clean damp cloth for cold compress can bring some relief.
  • Petroleum jelly or vaseline helps to ease discomfort. The jelly helps prevent cracking and serves as a protective barrier against external irritants.
  • Aloe vera gel generally used for sunburn can also help a cold sore to heal. According to studies, aloe vera gel has a significant inhibitory effect of 0.2-5% on HSV-1 growth (2).

Online Consultation

You can consult a health professional online and get the most efficient treatment according to your needs. Discussing with a doctor can help you understand the impact of cold sores on your health and what is the right approach to ease the symptoms.

On iLiveActive you can get yourself evaluated by answering a few queries. Our U.S. licensed physician will review your treatment request, follow up, and write an appropriate prescription.

Frequently Asked Questions

1. Are cold sores different from canker sores?

Canker sores are white lesions, occur commonly inside the mouth, and unlike cold sores, they are not contagious. The definite cause of canker sores is not known, frequently listed causes include stress, vitamin and mineral deficiencies, injury due to scraping of mouth with your toothbrush or a sharp food, and astringent chemicals in foods such as lemons. Canker sores heal on their own within two weeks.

2. What are the symptoms of genital herpes?

The symptoms of genital herpes are typically mild. In a standard case, individuals have a group of blisters or genital ulcers. These may burn and can be painful. It is also accompanied by burning sensation while urinating, itching, or discomfort in the genital area. Read more on genital herpes here.

3. Are these antiviral drugs safe during pregnancy?

These medications are used to treat genital herpes during pregnancy. Studies have shown that the use of acyclovir or valacyclovir is not associated with any increase in birth defects (3).

4. Is it possible to prevent transmission to my partner?

If one partner has recurrent herpes and the other partner is uninfected, treatment can be used to prevent the transmission.  By treating the infected person with suppressive medication, the transfer of infection can be prevented. Suppressive therapy with acyclovir can avoid or delay up to 80% of recurrences, preventing the transmission by 90% (4) (5).

5. Is herpes infection related to HIV?

Different viruses cause HIV and herpes, but patients affected by these viruses can transmit the infection to their partners. HIV results in an immunocompromised condition, which increases the risk of herpes infection.

6. Is there any chance of developing resistance to these medications?

Common drugs used to treat herpes are acyclovir, famciclovir, and valacyclovir. Resistance to these drugs is very rare. Generally, resistance occurs when the patient has weak immunity and has been treated for a prolonged period. According to studies, drugs like acyclovir have not been accompanied by detectable antiviral resistance in immunocompetent or immunocompromised populations (6).

Final Words

Cold sores are a herpes infection that can be recurrent, affecting your quality of life. Right medication and treatment guidelines can help you to prevent the outbreak and severity. If you are experiencing frequent cold sores, consult your doctor to understand the triggering factors and the needed treatment approach.

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