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Are Cold Sores Genetic? Who gets them and why

Key takeaways:
~ Cold sores are caused by the herpes simplex virus (HSV).
~ Less than half of people with HSV will get cold sores from the virus.
~ Genetics plays a role in who will get cold sores, and environmental factors can trigger the occurrence.

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What causes cold sores?

There are two types of herpes simplex virus: HSV-1 and HSV-2. Cold sores are usually caused by HSV-1, while HSV-2 usually causes genital herpes. But, either type of HSV can cause either condition.

image of the herpes simplex virus, which causes cold sores
Herpes Simplex Virus PMC8923070

Once the herpes simplex virus enters your body, it stays for life. It hides in nerve cells and can become active again later, causing another outbreak of cold sores.

Cold sores are highly contagious and can be easily spread through close contact, such as kissing or sharing utensils. If you have a cold sore, it’s important to avoid close contact with others, especially newborns, and to wash your hands frequently to prevent spreading the virus.

Using DNA from people who lived in the Bronze Age, researchers now think that HSV-1 has been making the rounds in humans for around 5,000 years.[ref]

Science of cold sores

Cold sores are also called herpes simplex labialis or fever blisters.

About 60%-80% of the population is seropositive for HSV1, but only around 20%-30% of the population will ever get cold sores. Some people get a cold sore rarely (once or twice a decade), while others may have monthly outbreaks.[ref][ref]

The sores that form on the outside or inside of the lip are uncomfortable — and embarrassing for some people. Who wants an open sore or big scab on their lip…

Typically, cold sores form when the HSV virus is actively replicating. Often people notice tingling or burning in the affected area before the development of the sore. Rupturing of the blister that forms will lead to a scab.[ref]

Why does this happen? The virus infects nerves around the mouth and remains latent in the nucleus of neurons, undetected by your immune system. When reactivated, the virus creates new infectious particles that move down the neuron to the skin, causing the sores.

Interestingly, the latent virus is thought to enhance the survival of the infected cells.

What causes the reactivation of the virus?

Triggers of HSV reactivation include:[ref]

  • stress, which can alter immune response
  • ultraviolet (UV) radiation (sunburn)
  • temperature fluctuations (cold, wind, heat)
  • surgical trauma or dental procedures
  • immunotherapy that suppresses the immune response
  • hormonal changes

Researchers find that HSV-1 reactivates in the trigeminal nerve when the immune system is suppressed, such as during times of stress or when fighting off another infection.

image showing the trigeminal nerve, which starts near the temple and spreads over the face and forehead
Trigeminal nerve illustration. (Public domain)


Why doesn’t everyone with HSV get cold sores?

This is a question that researchers have been trying to answer for decades.

Genetics is at least part of the answer as to why everyone doesn’t get cold sores. The strain of the herpes simplex virus may play a role as well. Additionally, an external stressor such as wind, sunburn, or oral surgery may need to be involved for some to activate the virus.[ref][ref]

Keep in mind that not everyone gets the herpes simplex virus. Transmission of the virus is usually through skin contact and is more likely if there is slight damage to the surface of the skin.[ref] Additionally, genetic variants in the immune response genes may protect some individuals from ever getting the virus.[ref]

Cold Sores Genotype Report:

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Lifehacks: Cold Sore Solutions

Talk with your doctor about the pros and cons of prescription-based antiviral medications for cold sores.

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Natural treatments for cold sores:

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About the Author:
Debbie Moon is the founder of Genetic Lifehacks. Fascinated by the connections between genes, diet, and health, her goal is to help you understand how to apply genetics to your diet and lifestyle decisions. Debbie has a BS in engineering from Colorado School of Mines and an MSc in biological sciences from Clemson University. Debbie combines an engineering mindset with a biological systems approach to help you understand how genetic differences impact your optimal health.