Do cold sores have any long-term health risks?

The herpes simplex virus (HSV) is a common sexually-transmitted virus. The name comes from the ancient Greek word “herpein”, meaning “to creep or crawl”, which is a nod to both the pattern of blister development as well as how successfully the virus has survived over time.

Two subtypes exist: HSV 1 and HSV 2, both of which are spread through close personal contact via mucous membranes — a less than pleasant term for the epithelial cells found covering the cheeks, tongue, and the glans (head) of the penis, as well as the vagina and rectum. HSV 1 and HSV 2 can both affect either the mouth or genitals, but HSV 1 causes oral herpes in over 90% of cases¹. HSV 1 and 2 are spread principally through exchange of saliva or through oral sex.

The classical course of an HSV flare is a mild flu-like illness, followed by tingling, itching or burning sensations where herpetic blisters are soon to form. Eruption of fluid-filled blisters occurs over affected areas, which pop and scab over before healing over two to four weeks, followed by a symptom-free period.

HSV 1 is very prevalent; close to four billion people worldwide under the age of 50 carry the virus,² many unknowingly due to infrequent or trivial symptoms. HSV oral blisters are commonly known as “cold sores”, which can be spread through oral sex to the genitals of the unaffected partner, causing HSV 1 genital herpes, a less severe variant of the illness.

Many people with genital herpes do not realise they are infected as they experience few or no symptoms

Transmission is more likely when cold sores are present, but the skin still sheds infectious viral particles even when lesions are absent. Interestingly, HSV 1 may be partially protective against HSV 2; the antibodies we develop provide cross-protection against both viral subtypes.³

In the UK, HSV 1 is the most common cause of genital herpes but HSV 2 is more likely to cause recurrent infections.⁴ Genital herpes is what most people commonly understand by the term “herpes”.

Once infected with a herpes virus the infection is lifelong; during quiescent phases HSV 1 typically resides in the trigeminal nerve, which supplies the face. Between outbreaks, HSV 2 tends to reside in the sacral ganglia, a cluster of nervous tissue around the tailbone.

Many people with genital herpes do not realise they are infected as they experience few or no symptoms.⁵ As with other sexually transmitted viruses (HPV, genital warts, hepatitis B) it’s a genetic lottery whose immune system can fight off the virus well enough to prevent symptoms.

Long term effects and treatment

As with many viruses, the body’s immune system is the best defence we have. No vaccine yet exists for HSV, and anti-viral medications are of limited benefit and not recommended for routine use, particularly in healthy people.⁶

HSV flares are self-limiting and only rarely scar, so the best advice is to make use of the simple painkillers paracetamol and ibuprofen during flares, and apply topical (liquid or cream) solutions to relieve pain.⁷ When persistent, severe or prolonged flares occur, a doctor may consider prescribing an oral antiviral such as valacyclovir, which has evidence for reducing the length of outbreaks.⁸

Barrier protection methods (like condom use) during sex can reduce transmission rates but provide imperfect protection

Those with genetic immune problems, or immunocompromising illnesses like HIV, are at an increased risk of complications of HSV. If HSV moves from the peripheral nerves up to the central nervous system (the brain), progressive confusion and loss of consciousness occurs. In these cases, prompt treatment with intravenous acyclovir in hospital minimises risk to life.⁹ Unfortunately, the general population also suffers from central nervous system HSV infection, though rarely (less than one in 100,000 people).¹⁰

The Roman emperor Tiberius outlawed kissing in public in an effort to halt an outbreak of herpes; not a bad guess considering the germ theory of disease was still a couple of thousand years away. To minimise your chances of contracting oral HSV, avoid kissing partners during a flare (when cold sores are visible), and limiting the sharing of mugs, lip balm, or water bottles with friends is a reasonable precaution.

Barrier protection methods (like condom use) during sex can reduce transmission rates but provide imperfect protection, as other skin-to-skin contact in the genital area, especially with friction, may transmit viral particles.¹¹

It’s also advisable to avoid sexual contact before, during, or immediately after your partner has active blistering lesions. This is possible if the partner in question experiences symptoms such as itching or burning that they can recognise as an imminent outbreak.

Pregnancy

In pregnancy, if you notice any symptoms that suggest genital herpes it is important to highlight this to the team monitoring your pregnancy; caesarean section is the safest way to deliver these babies,¹² especially when the diagnosis is in the final trimester.

The biggest risk factors for transmitting HSV from mum to baby include mum being HIV positive, which interferes with her immune response, and mum contracting HSV during pregnancy, especially the last trimester. In the majority of cases, the baby contracts HSV during passage through the birth canal,¹³ though transmission in utero can also occur.¹⁴

HSV is an extremely common virus with an undue social stigma. There are no failsafe ways to avoid the virus other than omitting all human contact

Unfortunately, infants are a group vulnerable to HSV infection due to their immature immune systems. Infant herpes can be limited to the skin, eyes and mouth, or may involve internal organs, especially the liver and brain. This can be fatal for babies, or cause long-term damage to organs involved. Risk factors for neonatal HSV, that is primary herpes infection during pregnancy, include young maternal age, first pregnancy, and receptive oral sex in the third trimester.

If HSV is acquired in the third trimester there is no time for the immune system to form the antibodies which normally circulate through the maternal bloodstream, placenta, and into the baby to provide a protective effect at birth. All this in mind, it’s important to remember that unless you have HSV blisters on your breasts or nipples (which is rare) breastfeeding your baby is still perfectly safe if you have HSV.

For new parents with recurrent genital herpes, the risk of HSV infection to their newborn is low, even if blisters are present at birth.¹⁵ Taking a drug called acyclovir from thirty-six weeks of pregnancy lowers the risk of outbreaks before delivery and hence the need for caesarean section.¹⁶

In summary, HSV is an extremely common virus with an undue social stigma. There are no failsafe ways to avoid the virus other than omitting all human contact. Either strain can be managed and outbreaks tend to become less frequent over time, so don’t despair if you have HSV — you are by no means alone.

Featured image is a close-up of a person’s lips, with one side visible and the other blurred

Last updated November 2022
Next update due 2025