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Cold sores

OVERVIEW

What is oral herpes?

Oral herpes is caused by herpes simplex virus infection (primarily herpes simplex virus type 1 / HSV-1), with a small portion possibly being early-stage herpes zoster. It often occurs during upper respiratory infections, high fever (axillary temperature of 39.1°C–41°C), or when the body's resistance is weakened, typically appearing at the corners of the mouth, lips, or nostrils—areas where skin and mucous membranes meet.

Initially, the affected area often experiences burning, itching, and redness, followed by clusters of pinhead-sized blisters that rupture, ooze, and eventually crust over as they dry.

The condition is self-limiting and contagious, with the entire course lasting about 1–2 weeks. Some patients may use topical antiviral medications for relief, but the disease cannot be cured—only managed—and tends to recur [1].

Is oral herpes common?

Yes. Oral herpes is primarily caused by herpes simplex virus type 1 (HSV-1). According to statistics, an estimated 3.7 billion people under the age of 50 worldwide are infected with HSV-1, accounting for 67% of the population in this age group. In other words, 67 out of 100 people under 50 are infected with HSV-1 [2].

Thus, oral herpes is quite common, though there is currently no precise incidence rate.

SYMPTOMS

What are the common manifestations of oral herpes?

Most oral herpes infections are asymptomatic, and many HSV-1 carriers are unaware they have the virus. Specific manifestations include:

  1. Herpes around the lips: Blisters typically appear at the corners of the mouth, lip borders, nostrils, or other skin-mucosa junctions, usually without systemic symptoms [1]. A history of contact with herpes lesions or prior outbreaks often precedes the onset.
  2. Itching and pain: Initial symptoms often include burning, pain, itching, and redness in or around the mouth. Within 1–2 hours, clusters of pinhead-sized blisters or open sores (ulcers) may form[1].
  3. Blisters prone to rupture: The small, clustered blisters may rupture, leading to erosions, oozing, and eventual crusting. The entire process lasts about 1–2 weeks, healing without scars but may leave temporary pigmentation[1].

After the initial infection, blisters or ulcers may recur periodically. The frequency of recurrence varies among individuals.

CAUSES

What are the common causes of cold sores?

Cold sores are caused by herpes simplex virus infection[3]. Humans are the only natural host of the herpes simplex virus, which exists in the blister fluid, saliva, blood, genital secretions, and feces of patients, recovered individuals, or healthy carriers[1]. They often occur due to factors such as colds, fever, fatigue, lack of sleep, depression, high stress, or anxiety, which weaken the immune system[1,3].

Are cold sores contagious?

Cold sores are contagious and can spread through direct and indirect contact.

  1. Direct contact transmission: For example, habits like nail-biting or thumb-sucking during a herpes simplex virus infection can lead to finger infections; breastfeeding mothers with infants suffering from herpetic stomatitis may develop nipple infections; facial contact among athletes can also cause infections.
  2. Indirect contact transmission: Mainly through saliva or genital secretions. Damaged skin or mucous membranes are more susceptible to infection. The virus enters the body through the nasal cavity, throat, conjunctiva, genital mucosa, or broken skin, replicates at the entry site, and causes local lesions, or spreads to other areas via the bloodstream or neural pathways[1].

Who is more likely to get cold sores?

  1. Newborns, severely malnourished children, or children with other illnesses: Children have weaker immune systems and are more susceptible to herpes simplex virus infection, leading to cold sores.
  2. Elderly individuals: Due to declining bodily functions and weaker resistance, the elderly are more prone to cold sore infections.
  3. People with compromised immune systems: Conditions such as HIV infection, malignancies, or organ transplants that weaken immune function increase susceptibility to herpes simplex virus and the likelihood of developing cold sores.

DIAGNOSIS

What tests are needed for oral herpes?

In most cases, a diagnosis can be made based on the patient's clinical manifestations. If necessary, tests such as vesicle fluid smear, culture, inoculation, immunofluorescence examination, and serum immune antibody measurement can be performed to aid in diagnosis.

  1. Morphological examination: Smear to look for inclusion bodies, electron microscopy to check for immature viral particles in damaged cells, or directly search for viral particles in the vesicle fluid.

  2. Immunological examination: Antigen detection can be performed using immunofluorescence or radioimmunoassay, utilizing monoclonal antibodies against various antigens of the herpes simplex virus to identify specific antigens in damaged cells [1,3].

Which diseases is oral herpes easily confused with?

  1. Shingles: Both conditions present with facial herpes, burning or stinging pain in the affected skin, and post-healing pigmentation. However, shingles lesions and pain follow nerve distribution, usually not crossing the midline of the face. The herpes clusters are dense, the pain is severe, and the condition is more serious and prolonged. These can be differentiated based on clinical manifestations [3].
  2. Contagious impetigo: Both conditions involve facial blisters, erosion, exudation, and no scarring after healing, and both are contagious. However, contagious impetigo presents with distinct red halos around pustules, and the pus dries to form honey-yellow thick crusts. Scratching often causes adjacent pustules to spread or merge, which can be differentiated based on clinical manifestations [3].

TREATMENT

How to treat cold sores?

This disease is a self-limiting condition caused by herpes simplex virus infection, with a course of 1–2 weeks. It can resolve on its own, but treatment helps shorten the duration[1].

  1. Cold compress: Ice cubes or ice packs can numb the cold sores, relieving pain and itching symptoms;
  2. Antiviral treatment: Starting antiviral therapy within 72 hours of onset helps reduce the severity of the outbreak. Usually, only topical antiviral ointments are needed, such as acyclovir, famciclovir, or valacyclovir ointments[1];
  3. Over-the-counter pain relievers: For severe pain, OTC pain relievers like paracetamol or ibuprofen can alleviate the pain caused by cold sores.
  4. Other treatments: For patients with acyclovir-resistant cold sores, foscarnet sodium can be used. It works by blocking viral DNA replication to relieve symptoms[1].

Can cold sores be completely cured?

This disease is caused by herpes simplex virus infection and cannot be completely cured. However, patients can reduce outbreaks by boosting immunity[1].

Which department should I visit for cold sores?

Generally, patients can go to the dermatology department or the oral mucosal disease department.

DIET & LIFESTYLE

What should patients with oral herpes pay attention to in daily life?

  1. Maintain a balanced diet, supplement with various vitamins, avoid colds, staying up late, and emotional stress. Regular exercise can boost immunity and help reduce the occurrence of oral herpes.
  2. Keep the herpes area dry and clean, as a dry environment can prevent recurrence.
  3. Avoid squeezing the blisters to prevent worsening the infection.
  4. A moist environment promotes herpes simplex virus replication. Store toothbrushes in a dry place and replace them with a new one, changing again after the herpes has fully healed.
  5. During an oral herpes outbreak, avoid using lip care products, as they can keep the affected area moist, encouraging herpes growth and prolonging the episode.
  6. Discard lipsticks or lip products used before and during the outbreak to prevent reinfection by the virus.
  7. Oral herpes is caused by a contagious virus, so avoid kissing and sharing cups, towels, etc., during outbreaks [1].

PREVENTION

How to prevent cold sores?

Cold sores can be prevented by paying attention to the following aspects:

  1. Avoid infection: Avoiding direct contact with people who have cold sores is the most effective prevention method.
  2. Sun protection: Certain factors like excessive sun exposure are known to trigger outbreaks, so take preventive measures and use sun protection when going outdoors.
  3. Get enough sleep: Maintain a regular schedule, balance work and rest, as sufficient sleep helps boost immunity.
  4. Exercise regularly: Moderate exercise strengthens the body and improves immunity to resist viral infections.