What are cold sores and what can you do about them?

Key facts in short

• Symptoms: In the early phase, a sensation of tingling, itching or irritation emerges, eventually giving way to the development of highly contagious fluid-filled blisters and ultimately leading to crusting, with complete healing typically occurring within one to two weeks.
• Causes: A viral infection caused by herpes simplex type 1 (occasionally type 2); reactivated by factors such as illness, stress, hormonal fluctuations, sunlight or skin injuries.
• Diagnosis: Visual diagnosis suffices; a trip to the doctor's is only necessary in severe instances or for high-risk patients.
• Treatment: Healing occurs naturally; pharmacy creams and home remedies can, however, speed up the healing process.
• Preventative measures: For primary infection prevention: Minimise contact. For protection against renewed outbreaks: Strengthen your immune system.

Definition: What are cold sores?

Cold sores (technical term herpes labialis) typically result from a herpes simplex type 1 viral infection and are characterised by blister and crust formation along the junction between the lips and the skin. The viral disease is contagious and can reoccur at any time after primary infection. 

Frequency

Cold sores are very common. According to estimations, approximately 90 per cent of adults in Germany have antibodies against herpes simplex type 1 in their bloodstream. However, not all infected individuals actually experience cold sores: Only 20 to 40 per cent of virus carriers actually develop cold sores. 

Cold sore symptoms & course 

Individuals with prior cold sore experience can promptly identify the first signs. The disease usually runs its course in one to two weeks, with herpes blisters disappearing naturally. 

The stages of cold sores

Sufferers go through various stages during a cold sore outbreak. We have compiled the most common symptoms below and added images to illustrate them.

Initial stage

The incubation period, i.e. the time between primary infection and initial symptoms, typically spans three to seven days but can vary in duration. Many individuals sense an impending cold sore outbreak even before the actual blisters appear.

Cold sores can manifest in the affected area as follows:

• Tingling
• Itching
• Burning
• Stinging
• Tightness
• Numbness
• Skin redness
• Swollen lymph nodes

During the primary infection, non-specific symptoms such as fever, fatigue, nerve pain or headache may also occur.

Image 1: First sign of cold sores is skin reddening.

Main symptoms

The painful blisters commonly associated with cold sores typically emerge at the junction between the lips and the skin due to viral multiplication and the subsequent destruction of skin cells. When laughing, talking or touching them, they often burst, typically within one to two days, and ooze. Note: The fluid contained in the blisters is highly contagious.

The painful blisters can appear in the following places:

• On the lips
• Below the lips
• Inside the oral cavity
• Along the upper lip
• Along the lower lip
• On the surrounding skin (cheeks, nose, earlobes)

In severe cases, blisters can spread extensively, cause significant pain and be accompanied by pronounced swelling. Be extra careful if there are any blisters near your eyes. In the worst-case scenario, when the cornea becomes affected, there is a risk of potential visual impairment.

Image 2: Cold sores with blisters on the upper lip.

Healing

Once the blisters have burst, open sores develop, which then crust over. Similar to the blisters, the scabs may be very fragile and tear easily when talking or laughing, potentially leading to bleeding. The duration of the crusting stage can vary. Cold sores typically take one to two weeks to heal fully. 

Image 3: Crusted over herpes blisters on the upper lip.

Reactivation

Once cold sores, always cold sores – unfortunately, this holds true for many individuals who experience recurrent infections once or twice a year. Medical professionals refer to this as reactivation. In around five to ten per cent of individuals affected, cold sores can occur more than five times a year. Over time, however, the course of the condition tends to become progressively less severe. 

When are cold sores contagious?

Cold sores remain contagious as long as the blisters or scabs are still present. Affected individuals are no longer contagious only when both the scabs and the blisters have healed fully.

Restrictions in daily life

Individuals experiencing an acute infection can generally continue their daily routines as usual. A doctor's sick note is not necessary. However, many individuals find cold sores to be a psychological burden and may feel less attractive during the acute phase, prompting them to withdraw somewhat from social activities.

Moreover, individuals with this condition must follow specific hygiene measures to prevent infecting others. Find additional information about this topic in the section on preventive measures. 

Possible complications

Cold sores are typically not considered dangerous and tend to heal on their own. Nevertheless, complications can arise in certain situations: 

Super-infection: Additional bacterial infection

For instance, if bacteria enter the open sores of the burst blisters due to scratching, there is a risk of concurrent bacterial inflammation in addition to the cold sores. This is referred to as a super-infection. Given the weakened state of the immune system during a cold sore outbreak, bacteria can multiply more readily. This significantly disrupts the healing process of both the blisters and the sores.

Cold sores in babies and during pregnancy: What can you do?

Cold sores are usually harmless for babies. In exceedingly rare instances, mothers can transmit the herpes simplex virus to their unborn child in the womb, potentially resulting in deformities and other complications. However, this transmission occurs not through normal cold sores but in cases of a severe course when the herpes viruses are present in the mother's bloodstream, a condition known as herpes sepsis.

Far more common is the transmission of genital herpes to a newborn during childbirth. Expectant parents should exercise extra caution if they have known herpes infections, refraining from oral sex in the case of acute labial herpes or abstaining from sexual activity altogether if one partner is suffering from acute genital herpes.

In general, severe courses are most likely to occur in babies during their first eight weeks of life, as their immune systems are not yet fully developed. In the worst-case scenario, the infection can lead to a fatal outcome if it affects the baby's brain or central nervous system.

If you have cold sores, it is advisable to avoid kissing your baby or putting their dummy in your mouth, even if you are the parent. Additionally, it is crucial to prevent your baby accidentally touching the herpes blisters and to maintain regular and thorough hand hygiene.

Caution is also advised when breastfeeding: Mothers with cold sores can continue breastfeeding their babies but should use a mouthguard and always disinfect their hands. However, if herpes blisters have also formed on the breasts, there is a risk of infecting the baby. In this case, the mother should refrain from breastfeeding and instead pump and dump the breast milk until the scabs have completely healed, ensuring the virus is no longer contagious. Consult your midwife or gynaecologist for guidance on the most appropriate feeding method for your baby during the enforced break in breastfeeding. 

Cold sores with a weakened immune system

When the immune system is weakened, cold sore outbreaks become not only more frequent but also more severe.

The following individuals are at an increased risk of experiencing a severe infection:

• People with HIV
• Patients undergoing chemotherapy or those with a history of cancer in general
• People with eczema
• People with atopic dermatitis or severe burns
• People who have just had surgery
• People with blood disorders
• People who take immunosuppressive medications (for example, after an organ transplant)
• Older people

Severe course: Herpes encephalitis

In exceedingly rare instances, herpes can spread throughout the entire body and potentially reach the brain, leading to encephalitis, a life-threatening condition. In this case, immediate medical care and fast treatment are required.

In the first few days, herpes encephalitis manifests with non-specific flu-like symptoms. A brief period of improvement is typically followed by the sudden onset of fever, accompanied by headaches and vomiting. As the disease progresses, those afflicted often deteriorate to the point where they exhibit severe illness. Impairment of speech, mild paralysis and even epileptic seizures are possible. Without treatment, herpes encephalitis can lead to an increase in intracranial pressure, potentially resulting in a loss of consciousness or even a coma. 

Causes: How are cold sores transmitted and how do outbreaks recur?

Cold sores can manifest during the primary infection with the herpes simplex type 1 virus (occasionally type 2) or be reactivated by specific factors in previously infected individuals. 

Primary infection with cold sores

The majority of individuals contract the herpes virus during childhood, usually before the age of six. The virus can be transmitted among young children at nursery school or be caught at home. It spreads by smear or droplet infection. The infected person has either directly inhaled small droplets of saliva or come into contact with objects such as cutlery, glasses, cups or towels on which the virus can survive for up to two days. A tender good-night kiss from parents can also be a source of infection. During teenage and adult years, the primary infection can also be activated through activities such as kissing or oral sex.

Following infection, the virus travels along the nerve fibres to the spinal cord, where it lies dormant, akin to an appliance in standby mode, until it is triggered or reactivated. The first outbreak may not occur until several years after the primary infection. However, once cold sores have broken out, they can come back at any time. The virus remains in the body for life.

Risk factors for recurrent outbreaks of cold sores

Certain situations can awaken herpes viruses from their dormant state:

• Colds and flu-like infections accompanied by fever – hence the colloquial term cold sores
• Mental and physical stress
• Injuries around the lips – for example after a trip to the dentist
• Increased exposure to sunlight or sunburn
• Irritation of the skin – for example through intensive kissing
• Medical use of cortisone-containing drugs
• Hormonal fluctuations

Diagnosis: When should you consult a health care professional?

In general, cold sores typically do not necessitate medical attention. Those affected are usually familiar with the course of the condition and know that cold sores typically heal up on their own. However, if the cold sores do not go away, it is wise to seek medical help.

This also applies in the following situations:

• During primary infection
• In case of uncertainty
• During pregnancy
• With newborn babies
• With a weakened immune system
• In case of blisters in the eyes or mouth, on genitals or in unusual places
• With atopic dermatitis and a severe bout of cold sores
• When generally feeling unwell with accompanying symptoms such as a headache and fever
• When experiencing multiple cold sore outbreaks in one year
• In case of unusually long-lasting cold sores

A trained medical professional can typically identify cold sores at a glance, often eliminating the need for further examinations. If there are complications, however, a doctor can take a swab sample and examine the virus.

Appropriate points of contact for medical concerns related to cold sores are:

• Family doctor
• Dermatologist
• Paediatrician
• Gynaecologist (for cold sores during pregnancy or genital herpes)

Treatment: What helps with cold sores?

Cold sores typically resolve on their own without the need for treatment. However, individuals affected by cold sores obviously want a speedy recovery. So what self-care measures can be employed for cold sores? Unfortunately, there is no universal remedy. Certain medications can, however, speed up the healing process to some extent.

Important: Never pop the herpes blisters! This will not accelerate the healing process. Quite the contrary: If the highly contagious fluid oozes out, it can lead to infection in other areas, thereby extending the healing period significantly.

Medications and medical aids

Individuals affected by cold sores can use creams, gels and ointments designed for cold sores to reduce the duration of the condition by approximately one day. To achieve the most effective outcome, these antiviral agents should be applied at the earliest sign of infection, such as tingling or a sensation of pressure. These remedies are usually available over the counter at pharmacies.

Popular products include:

• Valaciclovir
• Zovirax
• Valtrex
• Aciclovir
• Zovirax Duo (cream with aciclovir and hydrocortisone)

Certain active ingredients found in these creams are also accessible in tablet form for cold sore treatment. However, tablets are usually reserved for severe cases or for treating genital herpes. For common cold sores, healthcare professionals typically advise direct application to the affected area.

To both treat the open sore and to cover it, individuals can use a product known as a cold sore patch. The moist sore environment is believed to facilitate the healing process. Employing a heating pen is also said to accelerate the healing process by mitigating the inflammatory response.

Home remedies for cold sores

Some home remedies can alleviate cold sore symptoms and expedite the healing of the sores. Plant-based creams from a pharmacy (for example, containing lemon balm, sage or aloe vera) or zinc ointments can also be helpful.

However, which home remedy helps best against cold sores varies from person to person. Please do not combine several home remedies with each other as this could potentially result in unwanted interactions. If use of a home remedy makes cold sores worse, stop the treatment immediately. 

Cold therapy

As soon as the first signs appear, applying ice cubes is believed to both combat the spread of the virus and provide relief from early-stage cold sore symptoms.

Lemon balm

Lemon balm is believed to possess disinfectant properties, offering relief and potentially speeding up the healing process both before the outbreak and during the acute phase of cold sores. Simply rub two to four lemon balm leaves between your fingers and apply the extracted liquid directly to the affected area – this can be repeated up to ten times a day. Important: After touching cold sores, always wash your hands thoroughly to prevent spreading the virus and potentially infecting others.

Honey

Honey is believed to aid in wound healing and has been found to kill herpes viruses. Studies suggest that cold sores may heal approximately twice as fast when honey is used instead of the active ingredient aciclovir. Simply apply honey directly to the affected area with a cotton swab four times a day – ideally even before the actual outbreak occurs.

Black and green tea

The tannins found in black and green tea are said to inhibit the spread of viruses and promote cell formation, potentially aiding sore healing. Simply place a cool tea bag directly on the affected area several times a day and then discard it. 

Garlic

Owing to its active ingredient alliin, garlic is believed to possess antibacterial, antifungal and antiviral properties, potentially providing cold sore relief, particularly in the early stage. Simply crush one or two cloves of garlic and apply the resulting paste directly to the affected area using a cotton swab. Leave it on for ten minutes and then remove it – repeat this process up to five times a day. 

Tea-tree oil

The essential oil of the tea tree is said to possess anti-inflammatory properties and the ability to inhibit the spread of the virus. At the same time, tea-tree oil is believed to facilitate blister healing. Important: The oil must be diluted with another oil or cream before use, as it can irritate the skin if undiluted. The diluted mixture is most effectively applied using a cotton swab to prevent direct contact with the cold sores.

Aloe vera

Aloe vera is said to have antiviral properties, which may contribute to its ability to combat herpes viruses. Moreover, the plant is a popular home remedy for numerous skin issues. Aloe vera gels and aloe vera juice directly from the plant are equally effective for treating cold sores. Simply cut open a leaf, extract some juice using a cotton swab, and apply it directly to the affected area – this can be repeated up to three times a day. 

Is toothpaste suitable as a home remedy?

Some online sources promote toothpaste as a home remedy for cold sores. This advice is, however, outdated. It is now understood that toothpaste is not a suitable treatment for cold sores because it can dry out the skin, potentially impeding the healing process.

Alternative treatments

Some people also swear by homoeopathic remedies as a treatment option for cold sores. For example, globules containing Rhus toxicodendron can be used. In this case, it is best to seek advice from an alternative health practitioner. However, please keep in mind that there is no scientific evidence to back up the effectiveness of homoeopathic treatments.

In naturopathy, cold sores are also associated with a psychosomatic or spiritual meaning. For example, the outbreak of herpes is believed to signify a mental blockage that individuals can potentially overcome by identifying the underlying cause and addressing it. Accordingly, cold sores are thought to manifest primarily when conflicts remain unresolved and problems, for instance in relationships or at work, are not addressed. In naturopathy, it is believed that a conscious resolution of these ongoing conflicts can potentially decrease the frequency of cold sore outbreaks.  

Preventative measures: How can cold sores be prevented?

So far, there is no vaccination against cold sores. Therefore, you cannot completely protect yourself from the viral disease. In the context of preventing cold sores, it is important to differentiate between preventing the primary infection and preventing any recurrence (reactivation) of the virus.

Preventing the primary infection: Minimise contact

Since the herpes simplex virus is transmitted via smear or droplet infection, the only way to protect yourself is to reduce contact with infected individuals. In this regard, the primary responsibility falls upon the acutely infected person, especially when they have visible blisters or scabs around their mouth.

You can protect those around you from infection if you have cold sores by adhering to the following measures:

• Avoid physical contact, particularly with vulnerable groups such as babies, young children, the elderly, individuals with compromised immune systems and those with underlying health conditions.
• Do not kiss anyone during the acute phase, including your partner or your child.
• Do not share cutlery, plates, glasses, cups, towels and lip care products with other people.
• If possible, use cotton swabs to apply creams and discard the swabs promptly to avoid contamination.
• Wash and disinfect your hands after touching your lips.
• Regularly clean shared household items, along with door handles and taps.
• Refrain from sports that involve close physical contact.
• Abstain from oral sex.

Preventing reactivation: Strengthen your immune system

If you are already infected with the herpes simplex virus and experience frequent cold sores, you can strengthen your immune system and reduce the likelihood of outbreaks by implementing the following measures:

Immune-boosting diet

Cold sores tend to manifest particularly when the immune system is compromised, often with a sudden outbreak of the infection. Fortunately, we can take steps to boost our own immune system. Here are a few tips on how you can prevent cold sore outbreaks:

• Limit your sugar intake as much as possible: Sugar promotes numerous inflammatory processes and weakens the immune system.
• Aim to lose some weight if you are overweight: Excess abdominal fat releases hormones that compromise normal functioning of the immune system.
• Eat lysine-rich food: The amino acid lysine inhibits the spread of herpes viruses. Lysine is mainly found in eggs, lean meats, fish (except tuna), dairy products and tofu. It is also present in smaller quantities in legumes, fruit and vegetables.
• Avoid foods containing arginine: The amino acid arginine supports normal functioning of the immune system but also promotes the spread of herpes viruses. If you frequently experience cold sores, you should therefore minimise your intake of arginine-rich foods. Arginine is found in nuts, chocolates, wheat germ, tuna, oatmeal, unpeeled rice, peas and whole grain products.
• Eat food containing vitamin C: Vitamin C is, for instance, contained in higher amounts in foods like peppers, broccoli, sea buckthorn juice, kale, Brussels sprouts, sauerkraut, oranges, lemons, kiwi and grapefruit.
• Eat magnesium-rich food: Fish, spinach, berries, bananas, quinoa, amaranth and soybeans
• Ensure sufficient zinc intake: Liver, lentils, yeast flakes, soybeans and quinoa
• Possibly take nutritional supplements for: Vitamin C, magnesium and zinc.
• Drink at least two litres per day: Water, unsweetened teas or broth.

Reduce stress

Psychological and emotional stress can put a strain on the immune system and serve as a direct trigger for cold sores. Many individuals experiencing cold sores often find themselves taken by surprise by a new outbreak, especially during periods of enormous stress and at the most inconvenient times.

So if you frequently experience cold sores and want to reduce your levels of stress to help prevent outbreaks, consider implementing the following stress-reducing measures:

• Moderate physical activity: Exercise is indeed beneficial for both the immune system and stress reduction – be it walking, gym workouts, swimming or cycling.
• Relaxation techniques: Incorporate relaxation breaks, such as yoga, meditation, a calming bath or a brief nap, into your daily routine to promote your well-being and to combat stress.
• Learn to manage stress: To keep a cool head in challenging situations, various techniques are available, including specialised breathing exercises.
• Resolve interpersonal conflicts: Almost nothing is more stressful than an unresolved conflict. To reduce your levels of stress in the long term, try to foster harmonious interpersonal relationships and consider seeking therapy when needed.
• Say "no" more often: Many people become stressed when they feel compelled to keep everyone happy. In the long run, attempting to please everyone is usually at the cost of your own well-being. If you want to minimise the frequency of cold sore outbreaks, prioritise clear and honest communication, learning to express your own needs and setting boundaries without hurting the other person.

Make sure you get enough sleep

Our immune system works best when we get a good night's sleep. In a study conducted by the University of Tübingen, researchers examined the impact of sleep deprivation on the normal functioning of T cells. These are immune cells responsible for combating pathogens. The result: After just three hours of sleep deprivation, normal functioning of the cells was impaired.  

Refrain from extensive sunbathing  

Intense sunlight from sunbathing is a known trigger for cold sore outbreaks in many individuals. Ideally, you should not lie in the sun for too long or – if you do not want to go without sunbathing completely – use high SPF sunscreen specifically designed for the lips.