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Valacyclovir (Valtrex) for Cold Sores: Dosage, Duration & More

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 6/07/2019

Noticed a cold sore forming? Cold sores are the result of the herpes simplex virus, or HSV. Most people under the age of 50 have the HSV-1 version of the herpes virus, which is the form that’s most commonly associated with cold sores.

Cold sores can often start as an itching, tingling sensation. Over the course of several days, this can turn into a blister, which eventually develops into an open sore. The sores usually remain for one to two weeks before slowly healing and fading from your face, without leaving a scar.

While cold sores aren’t deadly, they can be very annoying. They’re also very infectious, making an outbreak an irritating infection risk for your friends and family, as well as a hindrance on your social life.

Because cold sores are caused by the herpes virus, there’s no proven, long-term cure. Luckily, cold sores are easy to treat using readily available, affordable medication.

The most common medication used to treat recurrent cold sore outbreaks is valacyclovir. Below, we’ve explained how cold sores can develop, as well as the best ways to treat and control cold sore outbreaks using valacyclovir (Valtrex) and other antiviral medications.

How Do Cold Sores Develop?

Cold sores, or oral herpes, are caused by the herpes virus. Most cold sores are the result of an infection with HSV-1, the most common form of the herpes simplex virus. Although it’s far less common, it’s also possible for HSV-2 to infect the mouth and cause cold sores to develop.

Most people with oral herpes will first notice cold sores as part of a primary herpes outbreak. In a primary outbreak, you’ll usually notice sores developing around your lips and mouth. There’s also a possibility of flu-like symptoms, such as fatigue, glandular swelling and muscle aches.

This outbreak happens just after you’re infected with the virus. Because your body hasn’t had enough time to prepare its own immune response to the virus, the first outbreak of cold sores tends to be the worst, both in terms of cold sores and other physical effects.

Over time, cold sores can come back. After the first infection, the herpes virus can live in the nerve ganglia near your cheek bone. When the virus is reactivated, it can spread back to the tissue around your lips and mouth, causing another outbreak.

About 40% of people who catch HSV-1 will develop recurrent cold sores. For others, the virus can remain dormant for life after the initial outbreak.  

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Cold Sore Outbreak Triggers

Cold sore outbreaks often occur at random, without any obvious cause. However, outbreaks can also be caused by certain environmental triggers, such as feelings or exposure to extreme heat, sunlight or other weather conditions. Know cold sore outbreak triggers include:

  • Certain foods, such as spicy foods or foods that contain ingredients that irritate the lips and mouth. Some people believe salty foods and foods that contain arginine can also trigger cold sores.

  • Stress, tiredness and exhaustion. If you’re overworked or stressed due to a personal matter, there’s a possibility that it could trigger a cold sore outbreak.

  • Colds, fever and illness. Cold sores are often triggered by a flu, the common cold and other viruses.

  • Allergic reactions. If you’re allergic to pollen, grass, mold or certain foods, it’s important to understand that these allergies can potentially act as triggers for a cold sore outbreak.

  • Menstruation. Many women notice that cold sore outbreaks happen at the same time as their period, as menstruation can trigger stress and hormonal changes that cause cold sores to reappear.  

  • Sunburn. Skin irritation from excessive sun exposure can potentially trigger and outbreak of cold sores, making it important to stay safe and protected while in direct sunlight.

Treating Cold Sores With Valacyclovir

The human body develops its own immune response to herpes, allowing it to control some of the effects of recurrent outbreaks. Most people notice that outbreaks get less intense as time goes on -- usually, the initial outbreak is the worst, then recurrent outbreaks aren’t so bad.

This immune response means that cold sores will heal on their own over the course of two to three weeks without the use of medication.

For faster healing, the best approach is to use an antiviral drug like valacyclovir to control the outbreak and prevent further spread of the virus.

Valacyclovir works by stopping HSV-1 and HSV-2 from spreading within the body. By stopping the virus in its tracks, even a relatively short course of valacyclovir can speed up healing and help you get rid of cold sores faster than they’d disappear naturally.

Valacyclovir is a prescription medicine, meaning you’ll need to talk to your doctor about using it as a treatment for cold sores. It’s safe, well tested and highly effective for HSV-1 and HSV-2.

Typically, the dosage of valacyclovir for cold sores is 2,000 mg of the drug taken once every 12 hours for two total doses. This high-dose, short-duration approach is scientifically proven to cut down the amount of time required for cold sores to heal and disappear from the face.

Depending on your symptoms and/or the severity of your cold sore outbreaks, your doctor might recommend a different valacyclovir dose. Follow your doctor’s instructions when using this drug for optimal safety and effectiveness.

If you get frequent outbreaks or have concerns about spreading HSV-1 or HSV-2 to others, your doctor may also recommend taking valacyclovir for ongoing suppressive therapy. You can learn more about this in our guide to valacyclovir dosages.

Your doctor might also recommend a different herpes drug, such as famciclovir or acyclovir. Our guide to acyclovir, famciclovir and other antiviral medications explains how these drugs differ, as well as the specific advantages and disadvantages of each medication.

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.