The Bottom Line

Herpes simplex virus (HSV) is one of the most widespread infections in the world—60–90% of adults carry HSV-1 (the virus that causes cold sores), and 10–30% carry HSV-2 (the primary cause of genital herpes). Both types cause recurring outbreaks throughout life because the virus never fully leaves your body. Most people have mild or no symptoms between outbreaks. Antiviral medications (acyclovir, valacyclovir, famciclovir) do not cure HSV but shorten outbreaks, reduce recurrences by 70–80% with daily use, and lower transmission risk.

What Is Herpes Simplex Virus?

Herpes simplex virus (HSV) is a DNA virus that infects humans and remains in the body for life. After the initial infection, the virus does not disappear—it retreats to nerve cells near the site of infection, where it lies dormant. Periodically, the virus reactivates and travels back down the nerve to the skin, causing a new outbreak of blisters or sores.

There are two types:

  • HSV-1: Primarily causes orolabial herpes—cold sores and fever blisters on and around the lips. It is extremely common, affecting 60–90% of people by age 50. Most people acquire it in childhood through casual contact (a kiss from a family member, shared utensils).
  • HSV-2: Primarily causes genital herpes. Seroprevalence is 10–30% globally, acquired mainly in adolescence and adulthood through sexual contact. HSV-2 recurs more frequently and persistently than HSV-1.

There is overlap—HSV-1 can infect the genitals and HSV-2 can infect the mouth. In fact, about 15% of genital herpes cases are caused by HSV-1. Knowing your specific type matters for predicting recurrence patterns and guiding treatment.

Signs and Symptoms

About 60% of first-time HSV infections cause no noticeable symptoms. When symptoms do occur:

First outbreak (primary infection):

  • Prodrome: 24–48 hours of tingling, burning, or itching before blisters appear—experienced by about 80% of patients
  • Grouped small blisters on a red base, breaking within 24–48 hours to form shallow, painful sores
  • Healing with crusting and skin regrowth over 7–14 days
  • Systemic symptoms (fever, fatigue, swollen lymph nodes) in about 30–50% of primary cases
  • Children may develop gingivostomatitis: severe painful oral ulcers making eating very difficult

Recurrent outbreaks:

  • Shorter duration (5–10 days), fewer lesions, milder symptoms than the first outbreak
  • Reappear in the same area each time (same lip, same genital region) because the virus lives in the same nerve ganglion
  • HSV-1 typically recurs 1–2 times per year; HSV-2 recurs 4–5 times per year in the first year, declining over time
  • Common triggers: emotional stress, fever, sunlight (for lip HSV-1), menstruation (40% of women with HSV-2 notice this trigger), illness, and immune suppression

What Causes Recurrences?

After the first infection, HSV retreats to sensory nerve ganglia—the trigeminal ganglion for oral herpes, the sacral ganglia for genital herpes. There it remains in a latent (dormant) state, controlled by your immune system. When immune surveillance relaxes—due to stress, illness, UV exposure, hormonal shifts, or immunosuppressive medications—the virus reactivates, travels down the nerve, and replicates at the skin surface, causing a new outbreak. Understanding your personal triggers can help you start antiviral treatment early during the prodromal phase, when medication is most effective.

How Is HSV Diagnosed?

HSV is often diagnosed clinically from its characteristic grouped blisters on a red base. When confirmation is needed:

  • PCR (polymerase chain reaction): The most sensitive test (95%+ accuracy). Detects HSV DNA from a swab of an active blister. Results available within 24 hours. Can distinguish HSV-1 from HSV-2.
  • Viral culture: Gold standard historically, but less sensitive (40–80%) and takes several days. Best collected from a freshly opened blister.
  • Serology (blood test): Type-specific IgG antibody testing can confirm past HSV-1 or HSV-2 infection even without active sores. Useful for knowing your status. Note: antibodies develop over weeks, so a negative test too soon after first infection may not be accurate.
  • Tzanck smear: A quick microscopy test showing characteristic multinucleated giant cells. Non-specific (cannot distinguish HSV from varicella), low sensitivity. Rarely used now.

Treatment Options

Antiviral medications are the cornerstone of HSV management. They work by blocking viral DNA replication. They do not eliminate the virus, but they:

  • Shorten the duration of outbreaks by 1–3 days
  • Reduce severity and pain
  • Prevent new blisters from forming if started during the prodrome
  • Reduce the frequency of recurrences by 70–80% when taken daily (suppressive therapy)
  • Reduce asymptomatic viral shedding, lowering transmission risk

The three main antiviral options for HSV are:

  • Acyclovir: The original HSV antiviral. Effective but requires more frequent dosing (5 times daily for some indications). Also available intravenously (IV) for severe infections or immunocompromised patients.
  • Valacyclovir (Valtrex): A prodrug converted to acyclovir in the body. Better absorption means less frequent dosing (twice daily for most indications). Generally preferred over acyclovir for convenience.
  • Famciclovir (Famvir): Similar effectiveness to valacyclovir with comparable dosing convenience.

Timing matters: Starting treatment during the prodrome (the tingling and itching phase before blisters appear) gives the best results. Treatment started more than 24–48 hours after blisters fully form provides less benefit. Many patients are prescribed a supply to keep at home so they can start immediately at the first sign of an outbreak.

Special situations:

  • Immunocompromised patients (HIV, transplant recipients) may need higher doses, longer treatment courses, and sometimes IV acyclovir for severe episodes
  • HSV resistant to acyclovir (rare, mainly in severely immunocompromised patients) requires a different drug, foscarnet, under specialist care
  • Pregnant women with genital HSV are typically offered suppressive therapy starting at 36 weeks to reduce the risk of active lesions at delivery and the need for cesarean section

When to See a Dermatologist

  • You suspect you have your first HSV outbreak—starting antivirals early reduces severity
  • You are having frequent recurrences (6 or more per year) and would like suppressive therapy
  • Your outbreaks are unusually severe, prolonged, or not responding to treatment
  • You have any eye involvement with an outbreak (pain, redness, vision changes)—herpes keratitis is serious
  • You are immunocompromised and have an active HSV infection
  • You are pregnant with genital herpes and approaching your due date
  • You have a new partner and want to understand transmission risk and protective strategies

Frequently Asked Questions

How is HSV-1 different from HSV-2—and does it matter?

Yes, it matters for predicting what happens next. HSV-2 recurs much more frequently than HSV-1—about 4–5 times per year vs. 1–2 times per year—and more commonly causes genital disease. If you have HSV-1 genitally (from oral sex), you are likely to have fewer recurrences than someone with genital HSV-2. HSV-2 also has a slightly higher transmission rate. PCR testing or type-specific serology can tell you which type you carry.

Can I give HSV to a partner without having an active outbreak?

Yes. Asymptomatic viral shedding—where the virus is active on the skin without causing visible sores—occurs on 10–15% of days in people with HSV-2. Most new herpes infections are transmitted this way. Suppressive antiviral therapy reduces shedding and lowers (but does not eliminate) transmission risk. Combining suppressive therapy with consistent condom use provides the greatest protection.

Will herpes outbreaks get better over time?

Yes, for most people. The immune system gradually develops better control of the virus over years. HSV-2 recurrences average 4–5 per year in the first year and typically decline to near zero within 5 years for many individuals. Daily suppressive therapy can accelerate this process by keeping viral load consistently low. Some people stop suppressive therapy after 12–24 months and find their recurrences have decreased significantly.

Is neonatal herpes a risk during pregnancy?

Neonatal herpes—HSV infection in a newborn—is serious, with a 30% mortality rate if untreated and long-term neurological effects in survivors even with treatment. The highest risk is when a woman acquires HSV for the first time near the end of pregnancy, as she has not yet developed antibodies to protect the baby. Women with known genital herpes are typically offered suppressive therapy from 36 weeks gestation to reduce the risk of active lesions at delivery. Discuss your herpes history with your OB/GYN early in pregnancy.

References

  1. Looker KJ, et al. Global and regional estimates of prevalent and incident herpes simplex virus type 1 infections in 2012. PLOS ONE. 2015;10(10):e0140765.
  2. Wald A, et al. Reactivation of genital herpes simplex virus type 2 infection in asymptomatic seropositive persons. N Engl J Med. 2000;342(12):844-850.
  3. Corey L, et al. Once-daily valacyclovir to reduce the risk of transmission of genital herpes. N Engl J Med. 2004;350(1):11-20.
  4. Gnann JW Jr, Whitley RJ. Clinical practice. Herpes zoster. N Engl J Med. 2002;347(5):340-346.
  5. ACOG Practice Bulletin No. 220: Management of Genital Herpes in Pregnancy. Obstet Gynecol. 2020;135(5):e193-e202.

Trusted Resources

Always consult a board-certified dermatologist for diagnosis and personalized treatment recommendations.