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Can Sunlight Trigger an Oral Herpes Outbreak?

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 5/12/2020

Herpes outbreaks can be difficult experiences. Whether you have oral or genital herpes, there’s nothing enjoyable about the irritating symptoms and stigma that can come with an outbreak of cold sores or genital herpes lesions.

Herpes outbreaks can occur for a variety of reasons. Sometimes, they’re triggered by another illness that temporarily suppresses your immune system. In other cases, herpes outbreaks can develop on their own as the herpes virus goes from dormant to active within your body.

Some of the most common triggers for herpes include stress, which can weaken the immune system and make the herpes virus active within the body, and fever. Sexual activity can also trigger some herpes infections, particularly HSV-2.

However, one of the most common triggers for herpes is sunlight. Exposure to sunlight is a well known, scientifically documented herpes trigger that can draw the virus out of dormancy and lead to an outbreak, especially for people with the HSV-1 form of the virus.

In this guide, we’ll explain how sunlight plays a role in triggering herpes outbreaks, as well as steps you can take to treat herpes outbreaks and minimize your risk of triggering an outbreak through sun exposure.

How Sunlight Affects Herpes

Herpes affects everyone differently. Many people with HSV-1 are asymptomatic, meaning they have the virus but never experience outbreaks. Others experience occasional outbreaks, with the average frequency about once per year.

Outbreaks of HSV-2 — or genital herpes — are more common, with the average HSV-2 infected person experiencing several outbreaks per year.

Sunlight is a relatively common trigger for HSV-1, or oral herpes. Because the genitals are rarely exposed to sunlight, it’s not a common trigger for genital herpes.

The main reason sunlight can cause herpes outbreaks is because of the presence of ultraviolet (UV) radiation. Exposure to even relatively small amounts of UV radiation can affect the immune system, making viral activity (such as activity of the herpes virus) more of a problem.

Researchers also believe that exposure to UV radiation can actively stimulate the herpes virus and increase the likelihood of an outbreak, as the virus moves from the nerve ganglia into cells on the lips and mouth.

Simply put, spending more time in the sun can affect your immune system and potentially trigger oral herpes outbreaks.

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Sunlight and Herpes Statistics

The idea that sunlight can trigger oral herpes is backed up by several studies. One study carried out by researchers at Kobe University Graduate School of Medicine found that 10.4 percent of people with HSV-1 claimed that their outbreaks occurred after exposure to the sun.

Interestingly, the number of people who reported outbreaks almost doubled during the summer months, during which the weather was warmer and sunnier. Compared to the normal 10.4 percent of participants, 19.7 percent reported oral herpes outbreaks during the summer period.

Younger participants were even more likely to experience oral herpes outbreaks during summer, with 28 percent of people aged under 30 reporting outbreaks during the warm, sunny weather of July to August.

Although this study didn’t analyze genital herpes, data from other studies shows that outbreaks of genital herpes are also more likely to occur after exposure to UV light.

For example, a one study noted that patients with genital herpes — in this case, on the buttocks — were likely to experience outbreaks shortly after being exposed to artificial UV light.

In short, exposure to UV rays, of which sunlight is the main source, could increase your risk of experiencing an outbreak if you’ve got HSV-1 or HSV-2.

How to Reduce Your Risk of a Sunlight-Triggered Outbreak

If you have HSV-1 or HSV-2, the most effective way to lower your risk of experiencing outbreaks is to avoid sunlight.

Obviously, this isn’t completely possible for most people. Even if you deliberately avoid going in the sun, your face and body will still come into contact with direct sunlight throughout the course of the day.

However, there are several steps you can take to lower your risk of triggering a herpes outbreak after sun exposure:

  • Avoid spending large amounts of time in direct, bright sunlight. As a general rule, if there is a risk of extended sun exposure causing sunburn, there’s also a risk of it triggering an outbreak of herpes.

  • Going out in the sun? Consider wearing a hat to shield your face from direct sunlight and prevent your lips from coming into direct contact with ultraviolet rays.

  • Use sunscreen to protect yourself when you’re at the beach, at the park or in any other setting with strong, direct sunlight. While the evidence for sunscreen protecting against herpes outbreaks is mixed, it’s still a good idea to keep your skin protected.

  • Consider wearing long pants and long-sleeved shirts during summer to avoid exposing more skin than necessary to direct sunlight.

  • Avoid using tanning beds and other devices that produce UV radiation, as this can lower your immune system and make herpes outbreaks more likely.

What to Do if You Experience Sunlight-Triggered Outbreak

Spent too much time in the sun? Herpes outbreaks triggered by sunlight produce the same type of symptoms as herpes outbreaks triggered by other events, making it best to treat them using a similar protocol.

The most effective way to treat an oral or genital herpes outbreak is through the use of antiviral medication like valacyclovir. Our guide to valacyclovir explains how this drug works, as well as how it can help you speed up healing and recovery during an oral or genital herpes outbreak.

If you experience frequent outbreaks as a result of sun exposure, it’s also worth talking to your healthcare provider about the use of drugs like valacyclovir or acyclovir as suppressive herpes treatment — a form of treatment that actively fights against herpes even when you don’t have symptoms.

Finally, if you experience frequent outbreaks after spending time in the sun, it’s worth changing your habits to make subsequent outbreaks less likely. The tips listed above can help to lower your risk of UV-related herpes outbreaks, making herpes easier to live with and manage.

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.