Herpes Labialis


Herpes labialis, also known as “cold sores”, is a common blistering viral infection of the lip or around the mouth.  Also known as fever blisters or herpes febrilis.

Herpes labialis is caused by the herpes simplex virus (HSV). HSV can produce primary (initial infection) and recurrent eruptions of herpes labialis. After the initial infection, HSV will remain within the sensory nerves of the individual. Recurrent eruptions of herpes labialis can occur in 20-40% of these individuals when the HSV reactivates or “wakes up” from its resting state.

Most of the primary herpes labialis infections are silent with nil or mild symptoms. However, occasionally, infections may present as mouth ulcers in children or upper respiratory tract infection-like symptoms in young adults. Pain on swallowing and drooling may occur when the infection becomes severe.

When recurrent herpes labialis occurs, groups of sores or blisters on an erythematous base, with crusting may occur on the border of the lips. It may also affect the skin around the month, inside the nose, cheek or inside the mouth. Ulcers inside the mouth, rather than on the lip, are more frequent in patients with low immune system.


HSV, especially the primary infection, can infect other body sites. Other organs can may be infected include the genitals (see herpes genitalis), nervous system/brain, eyes and prostate.

HSV can also cause other skin problems, including:

  • Eczema herpeticum: HSV complicating eczema
  • Herpetic whitlow: HSV infection of the fingers
  • Herpes gladitorum: HSV transmitted due to contact sports
  • Herpes simplex folliculitis: HSV infection of hair follicles

Neonatal HSV is a rare condition affecting newborns. Risk of transmission is highest for women with a primary HSV infection but can also occur in women with recurrent genital herpes. If you suspect your newborn to have HSV, he/she needs urgent medical attention.

The diagnosis can be made clinically by a medical professional. The diagnosis may be confirmed with a swab (HSV PCR) of fluids from the sore.

Mild sores of herpes labialis usually do not require treatment; however if treatment should be necessary, it is most effective when started early. It is often difficult to realise this on the initial infection but easier in future episodes.

As herpes labialis is a virus, antiviral medications can be used to treat them. Treating the sore would possibly help reduce the severity of infection and/or shorten the duration of discomfort. The antiviral medication (e.g. acyclovir, famciclovir, valaciclovir) may be used directly to the sores as a cream, taken by mouth (oral), or rarely, administered through the applied veins (intravenous). Oral/intravenous antiviral medications are recommended for patients with eczema, low immunity, a lot of pain, multiple cold sores, and prolonged outbreaks. Intravenous antiviral medications are generally reserved for very severe multi-organ infections. If you have lots of pain, additional pain killers and soothing skin treatments may also be prescribed. If your eyes are affected, it’s important to seek medical attention urgently.


Apply a cool wet compress or wash with salt-water and pat dry gently with a disposable paper towel followed by application of a greasy moisturiser like petroleum jelly

Symptoms improve as the sore scabs over a period of 7-10 days. The virus continues to stay in a dormant state. Some people get a single episode of infection only, while others can get recurrent infections. Certain factors that may increase the likelihood of recurrence include: infections like flu, acute stress or being tired, sunlight, skin injury or procedures like lasers.

There’s currently no licensed vaccine available for HSV. If you get cold sores often (i.e. over 6 times per year) or have a low immune system, long-term prophylactic antiviral medications may be prescribed. In Australia, prophylactic antiviral medication is only on the PBS for HIV-infected patients with AIDS or low immunity.

Prevention of transmitting herpes labialis

Herpes labialis can be spread to others when the sores are raw and not yet scabbed over.

Tips to prevent transmitting herpes labialis when the sores are active include:

  • Avoid close contact with individuals with low immune system, including those who are severely ill, newborns or elderly
  • Don’t kiss people, especially kids
  • Don’t share personal items such as lip balm, razors or communal towels
  • Avoid touching your cold sores; use disposable tissues when drying the area and discard by bagging or burning
  • Wash hands frequently

Figure 1. Herpes labialis on the border of the lips. Reproduced with the permission of Dr Tanumay Raychaudhury

This information has been written by Dr Cathy Zhao and Dr Tanumay

Published January 2020


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