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Will Valacyclovir Work After a Cold Sore Appears?

Mary Lucas, RN

Medically reviewed by Mary Lucas, RN

Written by Our Editorial Team

Last updated 5/12/2020

Cold sores can be a frustrating experience. At best, they’re an annoying symptoms of HSV-1 that can affect your appearance and self confidence. At worst, they’re a painful, burning pest that both hurts physically and affects your relationships.

They’re also exceptionally common. Data shows that around two thirds of all people aged from 14 to 49 have HSV-1, the variation of the herpes virus that can cause cold sores. While most of the people with HSV-1 are asymptomatic, many experience frequent cold sore outbreaks.

Luckily, cold sores are relatively easy to treat. Antiviral medication like valacyclovir (Valtrex) is highly effective against cold sores, helping to speed up healing and—if taken early enough in the development of a cold sore—potentially halt it in its tracks.

But is valacyclovir effective after a cold sore has had the chance to develop? In this guide, we’ll look at how you can use valacyclovir on existing cold sores to speed up recovery and lower the risk of your cold sore outbreak getting worse.

Using Valacyclovir Before a Cold Sore Develops

The most effective time to use valacyclovir for cold sores is before they have a chance to fully develop.

Usually, you’ll notice a cold sore a few days before it forms, or “erupts” out of the skin. Most of the time, cold sores begin as an itching, burning sensation on or around the lips. After a day or so, the itching skin develops a blister that eventually turns into an open sore.

If you notice and treat a cold sore with valacyclovir in the earliest stages, it will usually heal in a few days. Like with many other viruses, the sooner you act, the better. If you get recurrent cold sores, it’s worth keeping a supply of valacyclovir on hand for treating outbreaks as quickly as possible.

Our valacyclovir 101 guide contains more information on treating cold sores, including common valacyclovir dosage guidelines.

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Using Valacyclovir After a Cold Sore Develops

While valacyclovir is most effective the earlier you use it, it’s still highly effective for treating oral herpes after the cold sores have fully developed.

Studies show that valacyclovir significantly speeds up the healing process for cold sores, even if they’ve already developed and “erupted” around the lips and mouth. This means that it’s often a good idea to use valacyclovir if you have a cold sore, even in the later stages of its life cycle.

Not sure which stage your cold sore is currently in? Our guide to kissing and cold sores explains the eight stages cold sores go through and how each stage can affect treatment and healing.

Got a Cold Sore? Here’s What to Do

If you have a cold sore (or a larger outbreak of several cold sores), it’s worth seeking treatment even if the cold sores are fairly late in their life cycle. Cold sore outbreaks happen once per year on average, making it worth keeping a supply of antiviral medication on hand for next time.

The most effective treatment for cold sores is valacyclovir, which works by preventing the HSV-1 virus from spreading within the body. Used as part of a short-term treatment, it can speed up the speed at which cold sores heal, letting you avoid the discomfort and stigma of a cold sore.

Valacyclovir and other antiviral drugs can also reduce your risk of transmitting the HSV-1 virus to other people, making it easier to maintain a relationship if you frequently get cold sores.

Interested in using valacyclovir to treat cold sores? Your doctor can help you learn more about the valacyclovir side effects and benefits. Our valacyclovir dosage guide also includes a detailed section on valacyclovir doses for treating recurrent cold sores.

All in all, cold sores are certainly an annoyance. However, used effectively, antiviral medications such as valacyclovir can help you quickly deal with cold sores, no matter how much time they’ve had to develop,

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.