Herpes simplex, genital herpes, and herpes zoster: why do they appear, why do they come back, and how are they treated?

First: what does 'herpes' really mean?

In dermatology we mainly encounter two major situations. On one hand, herpes simplex, caused by the HSV-1 and HSV-2 viruses. And on the other, herpes zoster, caused by a different virus: the varicella-zoster virus (VZV), which is the same virus that causes chickenpox. Therefore, herpes zoster is not a 'stronger form' of cold sores — it is an entirely different virus.

HSV-1: the well-known cold sore virus

HSV-1 is extraordinarily common. The WHO estimates that around 3.8 billion people under the age of 50 — approximately 64% of that global population — are infected with HSV-1. Its classic manifestation is the cold sore: the typical sensation of tingling, burning and itching, followed by small blisters clustered around the lip. But HSV-1 does not live exclusively in the mouth; it can also cause genital herpes, particularly following oral-genital contact.

HSV-2: primarily genital herpes

HSV-2 is transmitted mainly through sexual contact and is one of the leading causes of recurrent genital herpes. The WHO estimates that around 520 million people between the ages of 15 and 49 are living with HSV-2. It can cause blisters, ulcers, pain, stinging, itching, pain when urinating and swollen lymph nodes; in a significant primary infection, even fever and general malaise. But there is something fundamental to understand: many infected people do not know they are infected, because they may never have had an obvious lesion, or may have had symptoms so mild that they mistook them for something else.

So, is HSV-1 oral and HSV-2 genital?

Not in absolute terms. It is a useful simplification, but not a perfect one: HSV-1 can be oral or genital, and HSV-2 is predominantly genital. The important difference is that when HSV-1 causes a genital infection, recurrences and viral shedding tend to be less frequent than with genital HSV-2. This affects the prognosis, the frequency of outbreaks, and the decision of whether or not to use suppressive therapy.

Why does herpes come back?

This is probably the most fascinating part. When the virus first enters the body, it infects skin or mucosal cells. It can then travel along nerve endings until it reaches the sensory nerve ganglia, where it remains dormant. We call this latency. The immune system keeps the virus under control, but does not eliminate it completely. That is why antivirals control replication but do not eradicate the latent virus.

The CDC clearly states that antivirals reduce symptoms and recurrences during treatment, but they do not eliminate the latent virus nor permanently change the risk of new recurrences once they are discontinued.

What causes it to reactivate?

There are various triggers: fever, infections, sun exposure, menstruation, stress, surgery, local trauma, or immunosuppression. The WHO recognizes several of these factors as known triggers of reactivation. And this explains something that many patients know all too well: 'every time I go skiing, I get a cold sore,' 'every time I'm under a huge amount of stress, it comes back,' or 'after the flu, it appears.' It's no coincidence.

The telltale tingling before the lesion

Many patients learn to recognize their own herpes. Hours before the blisters appear, they feel tingling, burning, itching, and sensitivity. This is called the prodrome, and it is a critically important moment, because antivirals for recurrences work best the sooner they are started. The WHO recommends initiating treatment for recurrences ideally within the first 48 hours, and the CDC indicate that with episodic genital herpes, the greatest benefit is obtained by starting treatment during the prodrome or on the first day of lesions.

How do we treat herpes simplex?

The classic antivirals are acyclovir, valacyclovir, and famciclovir. All of them work by inhibiting viral replication; they do not 'kill' the virus lying dormant inside the ganglion, but they do reduce the duration, intensity, and number of lesions, and in certain situations, transmission as well.

Cold sores: treating quickly makes sense

In a cold sore recurrence, starting treatment as soon as you notice the tingling or burning can reduce the duration and discomfort. The AAD also recommends initiating treatment as early as possible, even before the lesion is fully formed. In some patients, topical treatment may be sufficient, but in significant recurrent cold sores, oral treatments can be more effective.

What if I get cold sores constantly?

This is where the concept of suppressive therapy comes in: instead of waiting for each outbreak, the patient takes an antiviral every day. The goal is to keep viral replication sufficiently controlled to reduce recurrences. The AAD notes that in people with approximately six or more episodes of cold sores per year, a daily antiviral treatment may be considered. But there is no universal magic number: the severity, psychological impact, work situation, frequency, and whether episodes are very painful or debilitating also matter.

Suppressive therapy for genital herpes

Here we have even more evidence. In people with recurrent genital herpes due to HSV-2, daily suppressive treatment can reduce the frequency of recurrences by approximately 70–80% in patients with frequent recurrences. It can also reduce the risk of transmission to a susceptible partner. That does not mean zero risk, but it does mean a lower risk.

Is suppressive therapy for life?

Not necessarily; this is individualized. It can be used for months, years, or specific periods, and then we reassess, because the frequency of recurrences can decrease over time. The CDC recommend discussing periodically with the patient whether they wish to continue suppression.

And does genital HSV-1 always require suppressive treatment?

No. Compared to HSV-2, genital HSV-1 tends to recur less frequently and shed virus less often. That is why the CDC recommends reserving suppressive therapy for genital HSV-1 for people with frequent recurrences, through a shared decision-making process.

Can herpes be transmitted without having lesions?

Yes, and this is extremely important. HSV can shed asymptomatically: the skin looks completely normal, there are no blisters or pain, and yet viral shedding can still occur. This happens especially with genital HSV-2. Therefore, the absence of a lesion does not mean that transmission is impossible.

So, does a condom protect completely?

It reduces the risk, but does not eliminate it. Why? Because the virus can be shed from genital areas not covered by the condom. The WHO notes that condoms reduce the risk of genital herpes, but do not offer complete protection. In addition, when active lesions or prodromal symptoms are present, it is advisable to avoid sexual intercourse.

What about kissing someone with a cold sore?

When an active cold sore is present, especially with blisters, the risk of transmission is high. It is best to avoid kissing, oral contact, oral sex, and sharing objects that have been in contact with saliva. HSV-1 can be transmitted even without visible lesions, although the risk is higher during an active lesion.

Why should we avoid touching the lesions?

Because we can carry the virus from one area to another. We must especially avoid touching a lesion and then our eyes: ocular herpes can cause keratitis and potentially affect vision. A herpetic lesion near the eye warrants medical evaluation; the AAD recommends seeking consultation if herpes is near the eye, among other risk situations.

A special situation in patients with atopic dermatitis

Herpes simplex can spread over skin affected by atopic dermatitis and cause eczema herpeticum, which can present as multiple blisters or erosions, pain, fever, malaise, and rapid extension. This can be serious and requires early antiviral treatment. That is why a person with atopic dermatitis and extensive herpetic lesions should seek medical attention quickly; the AAD considers atopic dermatitis a reason to seek medical care in the setting of a cold sore.

Now let's talk about herpes zoster

Here we shift to a completely different virus. Herpes zoster is caused by the varicella-zoster virus — that is, the chickenpox virus. When you have chickenpox, the virus does not disappear completely: it also hides in nerve ganglia. And decades later it can reactivate. That is herpes zoster.

How does zoster present?

Classically, pain, burning, hypersensitivity, and tingling appear first. Afterwards, grouped, vesicular lesions develop on a reddened area, following the territory of a nerve. We call that territory a dermatome.

A very characteristic feature: it usually appears on one side

Shingles usually affects one or two adjacent dermatomes and generally does not cross the midline. It is very typical to see it as a unilateral band across the chest, back, abdomen, or face.

Why does it hurt so much?

Because the virus is reactivating inside a nerve. It is not simply a skin condition — it is also a neurological disease. That is why it can cause burning, electric shocks, stabbing pain, and extreme hypersensitivity. Even the brush of clothing against the skin can be unbearable.

One of the most important complications: post-herpetic neuralgia

After the skin has healed, the nerve may remain damaged. The patient then continues to experience pain, burning, electric shocks, and hypersensitivity for weeks, months, or even years. It is the most common complication of shingles, especially in older individuals.

Who is at greatest risk of shingles?

The risk increases with age, immunosuppression, certain treatments, cancer, and diseases that affect the immune system. The reason is straightforward: over time, our cellular immunity against VZV can decline, and the virus takes advantage of that loss of surveillance.

How do we treat shingles?

With the same major antivirals: acyclovir, valacyclovir, and famciclovir. Treatment is most effective when started as soon as possible, ideally within the first 72 hours. The CDC emphasizes that early treatment reduces new lesions, viral shedding, and the severity of acute pain.

What if more than 72 hours have passed?

That does not automatically mean 'there is nothing left to do.' Depending on the circumstances, treatment may still be indicated — especially if new vesicles are still appearing, there is ocular involvement, the patient is immunosuppressed, or the disease is extensive. This must be assessed on an individual basis.

Zoster on the face: this requires great care

Especially when it affects the forehead, eyelid, nose, or eye. Herpes zoster ophthalmicus can compromise the cornea, other ocular structures, and vision. The CDC stresses the importance of early diagnosis and treatment to prevent corneal progression and vision loss. For this reason, facial zoster near the eye warrants urgent evaluation.

What about the ear?

VZV can also affect nerves in the auricular region, causing ear pain, vesicles, facial paralysis, hearing disturbances, and vertigo. A well-known presentation is Ramsay Hunt syndrome, which also requires prompt evaluation.

Is herpes zoster contagious?

A person with shingles does not directly 'transmit shingles.' However, the blisters contain the varicella-zoster virus, and if someone who has never had chickenpox and is not immunized comes into contact with that virus, they may develop chickenpox. That is why it is recommended to cover the lesions and avoid contact with non-immune pregnant women, vulnerable newborns, or immunocompromised individuals until the lesions have crusted over.

Can shingles be prevented?

Yes, and this is a huge difference compared to herpes simplex. There is a vaccine, Shingrix, which is a recombinant vaccine. The CDC recommends two doses for adults aged 50 and older, and also for adults aged 19 and older who are immunosuppressed or have immunodeficiency.

Does the vaccine work well?

Very well. According to the CDC, in immunocompetent adults aged 50 to 69, efficacy against shingles was approximately 97%, and in those over 70, around 91%. It also provides very significant protection against postherpetic neuralgia.

Should I get vaccinated if I have already had shingles?

Yes, it may be indicated. Having had one episode does not guarantee it will never happen again. The CDC recommends Shingrix even for people who have already had herpes zoster, once the acute episode has resolved.

So, do HSV and shingles have anything in common?

Yes. Both share an extraordinary characteristic: neuronal latency. They enter, hide, remain, and can reactivate. But they are different viruses, they cause different diseases, and they have different prevention strategies.

Is there a vaccine for HSV-1 or HSV-2?

Currently, we do not have a vaccine for clinical use capable of preventing herpes simplex in a way comparable to Shingrix for shingles. Research continues, but today the strategy for HSV is based primarily on preventing transmission, episodic treatment, and suppressive therapy when indicated.

Why do some people have herpes outbreaks every month while others have one every ten years?

Because the relationship between the virus and the immune system is individual. Genetics, immunity, virus type, location, age, stress, sun exposure, illnesses, and treatments all play a role. Genital HSV-2, for example, tends to recur more frequently than genital HSV-1.

Is it always necessary to run lab tests to diagnose herpes?

No. Many lesions are clinically very characteristic. But when there is doubt, we can perform a PCR or take a direct sample from a lesion. The CDC considers that when a genital lesion is present, the clinical diagnosis should be confirmed whenever possible using a type-specific virological test. Serology has other indications and limitations.

A genital lesion is not always herpes

This is also extremely important. A genital ulcer or blister can have other causes: syphilis, trauma, aphthous ulcers, inflammatory dermatoses, infections, or other diseases. That is why you should not self-diagnose every genital lesion as herpes.

What if I am pregnant?

Genital herpes deserves particular attention during pregnancy. The risk of neonatal transmission is especially significant if a woman acquires a primary genital infection toward the end of pregnancy. For this reason, the obstetrician must always be informed of any history of genital herpes, and the management strategy during pregnancy and around the time of delivery is individualized.

Is herpes a 'serious' disease?

In the majority of immunocompetent individuals, no. Labial HSV is usually bothersome, painful, and recurrent, but is typically self-limiting. Genital herpes can have a significant physical and psychological impact, but effective treatments exist to control it. Zoster also tends to resolve. However, certain situations — ocular involvement, immunosuppression, extensive disease, neonates, encephalitis, or eczema herpeticum — can be potentially serious.

When would I seek medical attention promptly?

If herpes appears near the eye, with significant fever, very widespread involvement, in an immunosuppressed patient, during pregnancy, with intense neurological pain, with facial involvement, with visual disturbance, with ear involvement or facial paralysis, or on top of extensive atopic dermatitis.

What I want you to remember

When we talk about herpes simplex, we are thinking primarily of HSV-1 and HSV-2, which remain latent in the nerves and can reactivate. Antivirals such as aciclovir, valaciclovir, and famciclovir can treat recurrences or be used on a daily basis as suppressive therapy. In genital HSV-2, daily suppression can reduce recurrences by around 70–80% in people with frequent outbreaks and can also decrease transmission.

When we talk about herpes zoster, we are talking about the varicella virus, which reactivates years later in a nerve and can cause intense pain, vesicles in a dermatome, and, in some patients, post-herpetic neuralgia. Antiviral treatment must be started early and, unlike with HSV, we have a highly effective vaccine available to prevent zoster and its complications.

I am Dr. Florian Vallecillo, and if I want to leave you with just one idea today, it is this: herpes does not come back because it 'was not properly cured.' It comes back because these viruses possess an extraordinary characteristic: they know how to hide within our nervous system. Treatment does not consist of trying to 'remove the virus from the body,' but rather of blocking its replication when it awakens, reducing recurrences when they are frequent, limiting transmission, preventing complications, and, in the case of herpes zoster, preventing reactivation through vaccination when indicated. Because understanding why herpes comes back also allows us to understand why, in some patients, treating each outbreak is not enough and a true suppressive therapy can completely transform their quality of life.