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Sun and Herpes

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Sun exposure affects herpes negatively. Herpes outbreaks can be triggered by exposure to the sun.

The herpes simplex virus occurs in two forms. The first form of herpes is known as herpes simplex virus- 1, commonly known as oral herpes, or cold sores. The second form of herpes is herpes simplex virus- 2, commonly known as genital herpes.

Both forms of herpes are extremely contagious. Once a person has contracted either form of herpes, it stays in the body forever. During the first year of being infected with either oral or genital herpes, several outbreaks can be expected.

One of the scientifically documented triggers for herpes outbreaks is the ultraviolet light found in direct sunlight. The sun does negatively affect herpes outbreaks. Fortunately, there are specific treatments for sun exposure and herpes.

The Sun and Herpes

The frequency and severity of herpes outbreaks vary greatly from person to person. The sun may play a greater factor for some individuals than in others.

Scientists at the Sun Clinic and Sun Care Institute Osaka in the Department of Molecular Medicine at Kobe University Graduate School of Medicine in Japan evaluated the role of the UV radiation found in natural sunlight on oral herpes outbreaks.

During the study, the researchers found that 10.4% of the participants with herpes simplex virus- 1 flare-up said that the outbreaks were triggered by sun exposure.

However, during the summer months of July and August, reports of a sun-induced oral herpes breakout increased to 19.7% of the study population.

Also, for young people under the age of 30, 28% of the population experienced a herpes outbreak from the sun during July and August.

For young people under 30 who had been experiencing multiple outbreaks of oral herpes during the study, 40% of the patients experienced a sun-induced herpes outbreak in either July or August.

The scientists believe that the reason the sun triggers herpes outbreaks is due to the negative effect of ultraviolet radiation on the human immune system.

Another hypothesis is that solar ultraviolet radiation may stimulate the herpes simplex virus in nerve endings, called nerve ganglions.

Several other clinical studies confirm the fact that it is the ultraviolet radiation in sunlight that triggers herpes outbreaks in both oral and genital herpes.

A study published in the Journal of the American Academy of Dermatology reported exposing five patients with genital herpes on the buttocks to artificial ultraviolet radiation.

Four days after ultraviolet radiation exposure, the patients experienced a herpes outbreak eight out of the thirteen times they participated in the experiment.

The scientists concluded that direct exposure to ultraviolet light definitely triggers herpes outbreaks in experimental conditions. They recommended that patients with genital herpes should take preventative measures to avoid reactivating the virus.

Oral herpes and the sun

Both the New Zealand Dermatological Society and the Mayo Clinic agree that ultraviolet radiation from sun exposure can trigger recurrent outbreaks of oral and genital herpes.

Herpes sufferers can avoid direct sunlight, and may consider wearing sunscreen when going outdoors.

However, the medical journal Canada Family Physician published a 2008 clinical study stating that research on sunscreens had produced mixed results in herpes labialis (oral herpes) patients.

Sun protection which had worked in experimental conditions did not work as well in natural sunlight. In this particular study, oral antivirals were the treatments of choice.

Acyclovir for herpes and sun exposure

Acyclovir (Zovirax) is most often prescribed for herpes outbreaks, but penciclovir, valacyclovir, and famciclovir can be prescribed as an alternative.

These antiviral drugs shorten the duration of outbreaks and can lengthen the time between outbreaks, but do not get rid of the herpes virus permanently.

The Journal of Infectious Diseases suggests acyclovir as a treatment for genital herpes outbreaks due to ultraviolet radiation. This study noted that ultraviolet light was a “potent” trigger for herpes outbreaks.

During this study, patients with genital herpes were either given a placebo or 200mg oral acyclovir capsules five times a day, then exposed to ultraviolet light. Thirteen out of thirty- eight patients who received the placebo experienced herpes outbreaks.

Only three out of thirty- eight patients who were taking acyclovir experienced outbreaks of herpes. It took about five days for the outbreaks to occur after exposure to UV light. Interestingly, the outbreaks only occurred at the site of ultraviolet light exposure.

Once again, the research team recommended preventative measures for ultraviolet radiation exposure by staying out of the sun. The sun and herpes do not mix well.

Other suggestions for preventing herpes outbreaks

In addition to reducing sun exposure, there are other suggestions to help prevent herpes outbreaks and shorten their duration and intensity. Consider the following healthy options:

Healthy Options for Controlling Herpes Outbreaks
Eat a “clean” diet, such as a “caveman” style or vegan diet
Stop smoking, drinking alcohol, and eating sugar
Eat plenty of healthy fats from avocados, salmon, coconut, raw nuts, and seeds
Lysine is clinically proven to help improve herpes symptoms
Herbs such as lemon balm (Melissa), licorice root, and St. John’s Wort have also been clinically proven to help reduce herpes outbreaks
Relaxation techniques, such as meditation, yoga, tai chi, and qi gong help reduce stress which can trigger herpes outbreaks


Pubmed.gov, “Sunlight is an important causative factor of recurrent herpes simplex.” Ichihashi M, Nagai H, et al. Cutis. Nov 2004, 74(5Suppl): 14-8.

Pubmed.gov, “Reactivation of latent herpes simplex virus infection by ultraviolet light: a human model.” Perna JJ, Mannix ML, et al. Journal of the American Academy of Dermatology. September 1987; 17(3): 473-8.

Pubmed.gov, “UV light- induced reactivation of herpes simplex virus type 2 and prevention by acyclovir.” Rooney JF, Straus SE, et al. Journal of Infectious Diseases. September 1992; 166(3): 500-6.

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