Is the sun triggering your herpes outbreak?

Here’s why you might get more herpes outbreaks in the summer.

Updated: Wednesday 27 April 2022


sun triggering herpes outbreak

Oral and genital herpes can be unpleasant, and the stigma surrounding them doesn’t help either.

Herpes outbreaks can happen for a number of reasons. A weakened immune system, hormonal changes, and the common cold are all potential triggers for an outbreak to occur. The one trigger which might be surprising is the sunlight. Exposure to the sun can cause the HSV-1 virus to become active after staying dormant in the body causing a cold sore to develop. Oral herpes is common and it’s estimated that around 50-70% of the global population are affected, but thankfully it can be managed with the help of treatments like Aciclovir and Zovirax.[1]

How the sunlight affects herpes

Herpes affects people in different ways. Whilst some people are asymptomatic, meaning that they carry the HSV-1 virus but they don’t show any symptoms of it, others will experience frequent outbreaks.

The sunlight can trigger oral herpes, mainly due to ultraviolet (UV) radiation. Overexposure to UV radiation can affect the immune system, meaning it can no longer keep the HSV-1 virus controlled, causing cold sore outbreaks. Researchers believe that the virus moves from the nerve ganglia into the cells on the lips and mouth.

Outbreaks of the HSV-2 virus or genital herpes are less commonly triggered by sunlight as the affected area is not as exposed, but it can still occur.[2]

A study carried out by the Kobe University Graduate School of Medicine found that around 10.4% of those with the HSV-1 virus reported outbreaks. Interestingly, during the months of July and August, sun induced HSV-1 flare-ups increased to 19.7% overall, and 28% for participants under 30 years old.[3]

How to reduce the risk of triggering a sun induced outbreak

The most effective way to reduce a sunlight triggered outbreak is, unsurprisingly, to avoid sunlight. However, this might not be possible for most people, even if you try and intentionally avoid the sun you are still likely to come into contact with it at some point during the day.

Although the UV rays provide us with Vitamin D, long exposure in the sun can be harmful. If there is a risk of you catching sunburn, then you are at risk of a herpes outbreak. Although you can’t avoid the sun completely, there are many ways you can protect yourself after sun exposure:

  • Always use SPF before leaving the house. There is a tendency in the UK to only get the sun cream out if we’re going to the beach or doing some sunbathing, but sun protection is something we should all be applying to our skin daily for good skin health. If you are going somewhere where you’ll be exposed to the sun directly, either on a hot day or for long periods of time, bring sun cream with you to top up as needed. Moisturise your lips with lip balm containing SPF to help mitigate the effects of the dry climate on your lips.
  • Wear a hat to cover your face and lips from direct sunlight.
  • Avoid using tanning beds, sun beds or anything similar which produces UV radiation, as this can weaken your immune system, increasing the risk of a herpes outbreak.
  • Moisturisers containing tiger grass can be used on the face to increase protection from the sun. Use after sun, or a more natural substitute like aloe vera, after exposure to the sun to stop further irritating and damaging your skin.

How to treat a sunlight-triggered herpes outbreak

Sun induced outbreaks are likely to have the same symptoms as those caused by other triggers so the treatment protocol is usually the same. For oral herpes, symptoms usually manifest in the form of cold sores, starting with a tingling sensation and redness on the lips for a couple of days before forming painful, fluid-filled blisters on the edge of the lip which then scab over and heal after about five days or so. For genital herpes, symptoms include pain or itching, small red bumps or white blisters, and ulcers, in the vaginal area, penis, scrotum, buttocks, thighs, anus, and even the mouth.

For cold sores, Zovirax cream (aciclovir) is the best option for actively fighting outbreaks on the lip area. Other options include Compeed Discreet Healing Patches which provide a virus shield for the affected area. Antiviral treatments such as Aciclovir or Valaciclovir (Valtrex) can help to stop the spreading of HSV-2 by interrupting the replication of the virus, helping to reduce the duration of the infection. Although both treatments are not a cure for herpes, they can help to reduce the severity and length of the outbreak. If you have recurring outbreaks of herpes, the sun is something that you should definitely consider protecting yourself from - the previously mentioned Kobe University study found that sun-induced HSV-1 occured in 40% of patients under 30 years old in the summer months.

Toby Watson

Authored by Toby Watson

Pharmica Medical Writer


Toby (BSc) is an experienced medical writer, producing educational articles on many areas of health including sexual health, fitness, nutrition and mental health.

He particularly enjoys debunking misconceptions around heath conditions and their treatments, researching each topic in detail and writing easily-accessible content.

Herpes: do you need to tell your partner?
Herpes: do you need to tell your partner?