Cold Sores - Transmission, Symptoms and Treatment

Cold sores are a contagious disease caused by herpes simplex virus type 1 (HSV-1). Patients infected with the herpes simplex virus type 1 usually have painful sores on the lips, but the infection can also affect the gingiva, pharynx, tongue, roof of the mouth, inside the cheeks and sometimes the face the neck.

Labial herpes
Labial herpes

The herpes simplex virus type 1 can also cause lesions in the genitals, being transmitted through the practice of oral sex. However, genital herpes is more commonly caused by the herpes simplex virus type 2 (HSV-2), which is more easily multiplied in the skin of the genital region than in the oral cavity.

In general, 80% of cases of cold sores are caused by the herpes simplex virus type 1 and 20% by the herpes simplex virus type 2. The opposite occurs with genital herpes, where the herpes simplex virus type 1 causes only 20% of infections against 80% of the herpes simplex virus type 2.


The herpes simplex virus only causes disease in humans. Its transmission is by contact between people, through the saliva, periwinkles, skin or lips of the infected patient. When there are visible herpes lesions, the amount of virus in the oral cavity increases about 1000 times, which makes transmission at this stage much more likely to occur.

However, it is not only during colds that cold sores can be transmitted. From time to time the virus appears in the saliva, keeping the patient contagious for a few days, even when there is no active herpes lesion. If we randomly select 100 people with herpes simplex virus type 1, asymptomatic at the moment, we can find the virus in the oral secretions of up to 15 of them.

There are several forms of transmission of cold sores, in the most common adults are through kissing or cutlery and cups contaminated. However, most people become infected with the herpes simplex virus type 1 still in childhood, when contact with oral secretions is very common.


The incubation period for cold sores varies from 2 to 26 days, but in most cases lesions appear 4 to 6 days after contamination. However, it is worth noting that most patients do not develop symptoms after infection with the herpes simplex virus type 1. In fact, only 20% of people develop the disease. The other 80% remain with the virus "asleep" in the body for several years.

Primary infection with herpes simplex virus type 1

In about 20% of individuals who develop symptoms of cold sores, the first time the lesions arise, called the primary infection, is usually the one with the most severe symptoms. The patient may experience fever, malaise, loss of appetite, sore throat and enlarged lymph nodes in the neck. In children, gingivitis (inflammation of the gingiva) is common, while in the adult a strong pharyngitis with pus and ulcers in the pharynx and tonsils is the most common symptom of primary infection with the herpes simplex virus type 1. The picture usually lasts up to 2 weeks and disappears spontaneously.

Typical herpes lesions on the lips may not appear in the primary infection. When they appear, they are very painful.

The oral cavity is the site most affected by the herpes simplex virus type 1, however, dozens of other parts of the body can present the infection, including the hands, arms, neck, genitals and eyes. Herpes can also affect organs such as the brain (herpetic encephalitis), liver (herpetic hepatitis), lungs (herpetic pneumonitis), and esophagus (herpetic esophagitis). These organ lesions are usually severe and are more common in patients with some degree of immunosuppression such as HIV carriers, transplanted patients, or patients receiving chemotherapy or immunosuppressive drugs

Lip herpes

Once the primary infection has disappeared, the herpes simplex virus type 1 does not die, it remains alive in our body, asleep in the cells of our nerves, waiting for a low immune system to re-attack.

The typical lesions of cold sores appear in the reactivation of the virus. The picture is much milder than in the primary infection and usually lasts for a maximum of 7 days. Intense symptoms of primary infection such as fever and malaise are not common.

6 to 48 hours before the appearance of the labial lesions the patient may begin to receive signs that cold sores will arise. Usually this warning comes in the form of tingling, pain or itching on the lips.

Herpes simplex lesions initially appear as small reddish and painful elevations that quickly turn into pooled blisters. These blisters have seen small pustules (blisters with pus inside) and burst, turning into ulcers. Ulceration is the last stage of the active lesion, healing in a few days, in the form of crusts.

As already said above, many patients do not present the primary infection with herpes. This does not mean that the virus is not alive inside your nerve cells. If the patient exhibits a drop in immunity, and this can occur, for example, during periods of stress, cold sores may appear for the first time only years after the contamination. When the patient does not present the primary infection, it is almost impossible to determine the date on which the infection was contaminated.

Cold sores may have several recurrences for a year or only one or two for a lifetime. This frequency is determined by several factors, including the competence of the patient's immune system and the type of life it takes. As the years go by, the recurrences are getting weaker and smaller.


The diagnosis of cold sores is often made only with clinical data, by examining the lesions and evaluating the symptoms. In case of doubt, a sample of lesions can be collected for laboratory evaluation. The bubble phase is the one with the greatest presence of the virus, being the most indicated for the collection of the material.

Serology and PCR (virus DNA detection) can also be used to diagnose and distinguish herpes simplex virus type 1 and type 2 infections.


Whenever we talk about treating cold sores with infected patients, one question comes up: Does cold sore have a cure? Unfortunately, the answer is no, herpes has no cure. There is treatment, but it aims to reduce symptoms, accelerate healing and prevent complications. There is no remedy to cure cold sores. Escape the treatments that promise the cure of herpes, because there is no scientific study in the literature that shows that it is possible to cure cold sores with any type of treatment.

In primary infection, if treatment with antiviral tablets (aciclovir, valaciclovir or fanciclovir) is initiated within the first 72 hours, there is a significant reduction in disease duration and symptom severity.

In reactivating cold sores, treatment will depend on how frequent the recurrences and the intensity of the symptoms are.

Patients with rare and poorly symptomatic seizures may not require any treatment, at most some anesthetic ointment to reduce pain.

Patients with more frequent recurrences, especially those with pre-injury warning signs, may benefit from early use of antivirals. In general, the best results are obtained with oral medications, started as soon as possible after the first symptoms. The famous acyclovir ointments are less effective than the oral antiviral use. Acyclovir should be taken for five days, while new antivirals such as valaciclovir or fanciclovir are effective with only one day of treatment.

If the patient has more than 4 reactivations per year, or usually develops extensive, painful and aesthetically uncomfortable lesions, the daily use of antivirals for an extended period of time may be an option. Studies show that acyclovir or valaciclovir can be safely used continuously for more than a year.


There is no vaccine against herpes, so prevention should be based on the situations that usually trigger the seizures.

The most common trigger for reactivation of cold sores is usually intense sun exposure. Patients with a history of herpes should avoid spending hours in the sun. The use of sunscreen is essential and helps to reduce the appearance of the lesions. The use of the shield appears to be more effective than acyclovir ointment in preventing sun-induced cold sore recurrences.

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