Herpes simplex virus infections outside the genital tract are far more common and varied than most people realize. While the phrase “herpes” tends to conjure images of genital sores, the virus frequently sets up shop on the lips, inside the mouth, on the eyes, across the skin, and even within the brain and nervous system. HSV-1 is the dominant player at these nongenital sites, though HSV-2 occasionally shows up there too. The range of conditions the virus can cause, from a nuisance cold sore to a life-threatening brain infection, makes nongenital herpes worth understanding well beyond the basics.
Which Virus Type Drives Nongenital Infections
Both HSV-1 and HSV-2 can technically infect any mucosal or skin surface, but in practice they have strong site preferences. A six-year study of herpes cultures at a Kentucky medical center found that HSV-2 accounted for only about 9% of patients with nongenital herpes over the entire study period, confirming that HSV-1 is overwhelmingly the cause of infections outside the genital tract.1PubMed Central. Six-year study of the incidence of herpes in genital and nongenital cultures in a central Kentucky medical center patient population That same study noted HSV-2 remains primarily a genital pathogen, while HSV-1 has been expanding its role even into genital disease. For the purposes of nongenital herpes, though, HSV-1 is the virus you are almost certainly dealing with.
Latency and Reactivation
After an initial infection, HSV does not leave the body. The virus travels along nerve fibers to sensory nerve cell bodies, where it enters a dormant state called latency.2PubMed Central. The molecular basis of herpes simplex virus latency For orofacial and ocular infections, the virus typically parks itself in the trigeminal ganglion, a cluster of nerve cells near the base of the skull that serves the face. For infections on other parts of the body, nearby sensory ganglia serve the same purpose. The virus can sit quietly for months or years, producing no symptoms at all, before reactivating and traveling back down the nerve to cause a new outbreak at or near the original infection site.
Reactivation can be triggered by a variety of stimuli. Stress is one of the best-studied triggers: activation of the body’s glucocorticoid receptor during stress responses has been shown to accelerate viral reactivation from latency.3PubMed Central. Intimate Relationship Between Stress and Human Alpha‑Herpes Virus 1 (HSV‑1) Reactivation from Latency Other known triggers include fever, sunlight exposure, physical trauma, fatigue, and immune suppression. The pathways linking these stimuli to viral gene expression are varied and sometimes overlap, which partly explains why outbreaks can feel unpredictable.4PubMed Central. Strength in diversity: Understanding the pathways to herpes simplex virus reactivation
Orofacial Herpes
Cold sores on the lips are the most recognized form of nongenital herpes, but the virus’s oral territory extends well beyond the lip border. Primary herpetic gingivostomatitis, the first-time oral infection, is most common in children and presents with fever, swollen gums, and painful ulcers throughout the mouth. It typically resolves in 10 to 14 days, though serious complications like meningitis or encephalitis can rarely occur.5BMJ. Primary herpetic gingivostomatitis in children Adults can develop gingivostomatitis too, particularly if they were not infected during childhood and encounter the virus later in life.6Journal of Dentomaxillofacial Science. Primary herpetic gingivostomatitis in young adult
After the initial infection heals, recurrent cold sores tend to be milder and shorter-lived, but the virus continues to shed from the oral mucosa even between visible outbreaks. This asymptomatic shedding is remarkably frequent. One study of healthy adults found HSV-1 was detectable at oral sites on roughly a quarter of all sampled days, and of those positive days, over 94% occurred when participants had no visible lesions.7PubMed Central. Herpes Simplex Virus Type 1 Shedding in Tears, and Nasal and Oral Mucosa of Healthy Adults Another review using sensitive detection methods found HSV-1 DNA present in over half of seropositive patients across multiple visits, with a daily detection rate around a third of all days tested.8PubMed. Asymptomatic shedding of herpes simplex virus (HSV) in the oral cavity This means transmission can and does happen when someone has no sores at all, which is a key reason the virus is so widespread.
That said, the picture is not entirely bleak. A Japanese study using a different detection method found oral mucosal shedding in fewer than 3% of samples from immunocompetent adults, with shedding largely restricted to people with primary infections or compromised immune systems.9PubMed. Herpes simplex virus DNA testing by a loop-mediated isothermal amplification method for accurate clinical diagnosis and detection of mucosal viral shedding The discrepancy likely reflects differences in detection sensitivity and population characteristics, but it does suggest that the immune system keeps shedding in check for most healthy carriers, even if it cannot eliminate it entirely.
Ocular Herpes
When HSV reactivates along the ophthalmic branch of the trigeminal nerve, the eye itself can become involved. Herpes simplex keratitis, an infection of the cornea, is one of the leading infectious causes of blindness in developed countries. The disease can affect every layer of the cornea, from the outermost epithelium to the deeper stroma and endothelium. Recurrent stromal keratitis is especially damaging: the immune system’s inflammatory response to the virus in the cornea leads to scarring, blood vessel growth into tissue that should be clear, and progressive loss of corneal transparency.10PubMed Central. Pathogenesis of herpes simplex keratitis: The host cell response and ocular surface sequelae to infection and inflammation
What makes herpes keratitis particularly tricky is that much of the damage comes not from the virus itself but from the immune response it provokes. Research in mouse models has shown that the blinding corneal lesion is driven primarily by immune cells, and that molecules promoting blood vessel growth in the cornea play a critical role in disease progression.11PubMed. Mice transgenic for IL-1 receptor antagonist protein are resistant to herpetic stromal keratitis: possible role for IL-1 in herpetic stromal keratitis pathogenesis This is why treatment involves not just antiviral drugs but sometimes anti-inflammatory medications as well, though the balance between controlling the virus and calming inflammation requires careful clinical judgment.
Skin Infections Beyond the Mouth
HSV can infect skin at virtually any body site when the virus gains entry through a break in the skin barrier or through close skin-to-skin contact. Three distinct patterns stand out.
Herpes gladiatorum is the best-known example of skin-transmitted HSV. It spreads through the abrasive, sweaty skin contact of contact sports, with wrestling carrying the highest incidence.12Premier Journal of Infectious Diseases. Microbial Skin Infections in Contact Sports: Epidemiology and Prevention A classic outbreak at a high-school wrestling camp infected about a third of all wrestlers. Lesions appeared most often on the head, followed by the extremities and trunk, and restriction enzyme analysis confirmed that different viral strains were spreading independently within different weight classes.13PubMed. An outbreak of herpes gladiatorum at a high-school wrestling camp The attack rate among heavyweights reached two-thirds, likely because their practice group had more intense physical contact.
Herpetic whitlow involves HSV infection of the fingers or thumb, typically entering through a small cut or hangnail. It has long been recognized as an occupational hazard for healthcare workers, especially those who come into contact with patients’ oral secretions. A case report of a pediatrician who developed whitlow after a minor knife cut to his finger highlighted how unrecognized HSV infections in children’s mouths can become a source of exposure for clinicians.14PubMed. Herpetic whitlow infection in a general pediatrician–an occupational hazard The condition is painful and can be mistaken for a bacterial infection, which matters because incising a herpetic whitlow (as you would a bacterial abscess) can worsen it and spread the virus.
People with atopic dermatitis face a particular risk from a widespread HSV skin infection called eczema herpeticum. Their already-disrupted skin barrier can allow the virus to spread across large areas, sometimes requiring hospitalization. Research suggests that patients prone to recurrent eczema herpeticum have distinct inflammatory patterns in their skin that may alter barrier function and make the epidermis more susceptible to viral infection.15JID Innovations. Atopic Dermatitis Complicated by Recurrent Eczema Herpeticum Is Characterized by Multiple, Concurrent Epidermal Inflammatory Endotypes
Neurological Complications
The most feared nongenital herpes complication is herpes simplex encephalitis, a direct infection of the brain. Without treatment, mortality exceeds 70%, and only a tiny fraction of untreated patients regain normal brain function.16MedLink Neurology. Herpes simplex encephalitis – Section: Prognosis and complications Even with modern antiviral therapy, the disease often leaves survivors with lasting cognitive, memory, or personality changes. It is rare but not exotic: herpes encephalitis is one of the most common causes of sporadic fatal encephalitis in the developed world. It can result from a primary infection or, more commonly in adults, from reactivation of latent virus.
A less dramatic but noteworthy neurological condition is Mollaret’s meningitis, a pattern of recurrent episodes of aseptic meningitis that resolve on their own, often recurring three or more times. HSV-2 is the usual culprit here, making this an exception to the general rule that nongenital herpes is an HSV-1 story.17PubMed Central. Recurrent benign lymphocytic (Mollaret’s) meningitis due to herpes simplex virus type 2 The episodes themselves typically resolve without lasting damage, but the recurrence pattern can be alarming and diagnostically confusing until HSV-2 is identified as the cause.18PubMed Central. Mollaret’s Meningitis due to Herpes Simplex Virus 2: A Case Report and Review of the Literature
Bell’s Palsy and Erythema Multiforme
Some consequences of herpes infection are not caused directly by viral destruction of tissue but by the immune system’s response to the virus. Two conditions illustrate this well.
Bell’s palsy, the sudden one-sided paralysis of the face, has been linked to HSV-1 reactivation from the geniculate ganglion, a nerve structure involved in facial movement and sensation. A well-controlled study provided what its authors described as conclusive evidence that HSV reactivation from the geniculate ganglia is the most important cause of Bell’s palsy.19PubMed. Bell’s palsy and herpes simplex virus The connection rests on clinical, immunologic, and laboratory parallels between Bell’s palsy and known reactivation syndromes of herpes viruses.20PubMed. Herpes simplex virus in idiopathic facial paralysis (Bell palsy) Some debate remains, and not every case of Bell’s palsy is herpes-related, but the link is strong enough that antiviral medications are sometimes prescribed alongside steroids for treatment.21PubMed Central. Herpes simplex virus type 1 and Bell’s palsy-a current assessment of the controversy
Erythema multiforme is a skin reaction producing distinctive target-shaped red lesions, sometimes with mucous membrane involvement. HSV infection is its most common trigger. Researchers have found immune complexes containing HSV antigen and antibody circulating in the blood of affected patients, which likely play a role in driving the skin inflammation.22PubMed. Herpes simplex antigen in immune complexes of patients with erythema multiforme: presence following recurrent herpes simplex infection The proposed mechanism involves viral DNA being transported to skin sites by immune cells, where it triggers an inflammatory cascade when T cells recognize the viral proteins.23PubMed. Understanding the pathogenesis of HSV-associated erythema multiforme Interestingly, researchers have not been able to identify a clear difference in the herpes-specific immune response between people who get erythema multiforme after cold sores and those who have recurrent cold sores without this complication, so it remains unclear why only some people develop it.24PubMed. The herpes-specific immune response of individuals with herpes-associated erythema multiforme compared with that of individuals with recurrent herpes labialis
The Emerging Link to Alzheimer’s Disease
One of the more provocative lines of research in recent years involves a possible connection between HSV-1 in the brain and Alzheimer’s disease. The evidence is still accumulating, but it has moved beyond speculation. Multiple studies now report that HSV-1 viral proteins have been detected in brain regions affected by Alzheimer’s, and that infection is associated with the accumulation of amyloid-beta plaques and hyperphosphorylated tau, the two hallmark pathologies of the disease.25PubMed Central. HSV-1 as a Potential Driver of Alzheimer’s Disease
Laboratory work has sharpened this picture. In a three-dimensional model of human brain tissue, researchers found that latent HSV-1 could be reactivated by repeated mild mechanical injuries, and the reactivated virus drove the production of amyloid-beta and phosphorylated tau, along with destructive neuroinflammation.26PubMed. Repetitive injury induces phenotypes associated with Alzheimer’s disease by reactivating HSV-1 in a human brain tissue model The risk appears to be genetically influenced: carriers of the APOE4 gene variant, already the strongest known genetic risk factor for late-onset Alzheimer’s, seem especially vulnerable to HSV-1-driven pathology. Separately, researchers demonstrated that HSV-1-infected neurons can spread phosphorylated tau to neighboring cells through small secreted particles, suggesting a mechanism by which localized infection could propagate tau damage across brain regions.27PubMed Central. HSV-1 infection induces phosphorylated tau propagation among neurons via extracellular vesicles
None of this proves that HSV-1 causes Alzheimer’s. The virus infects the majority of the world’s population, and most people never develop dementia. But the convergence of epidemiological, genetic, and laboratory evidence is enough that several research groups are now investigating whether antiviral treatment or future HSV vaccines could reduce Alzheimer’s risk in susceptible populations.
Antiviral Resistance
Standard treatment for herpes infections relies on drugs like acyclovir and its derivatives, which work by targeting the viral enzyme thymidine kinase. These medications are effective at reducing symptom duration and outbreak frequency, but they cannot eliminate the latent virus hiding in nerve ganglia. For most healthy people, resistance is not a practical concern. The problem arises mainly in immunocompromised patients who require prolonged antiviral therapy.
Resistance develops through mutations in the thymidine kinase gene. Research on HSV-1 has shown that mutations in both conserved and non-conserved regions of this gene can confer high-level resistance to acyclovir.28PubMed Central. Thymidine kinase mutations conferring acyclovir resistance in herpes simplex type 1 recombinant viruses In HSV-2, prolonged acyclovir treatment has been shown to select for resistant isolates carrying mutations that effectively shut down the thymidine kinase gene entirely.29PubMed. A point mutation in the thymidine kinase gene is responsible for acyclovir-resistance in herpes simplex virus type 2 sequential isolates When resistance does develop, treatment options become limited. Alternative drugs like foscarnet and cidofovir exist but carry more side effects and are usually reserved for serious infections in transplant recipients or people with advanced HIV.
Gene Editing and the Prospect of a Cure
Every current herpes treatment is suppressive, meaning it manages symptoms and reduces viral shedding but cannot touch the latent virus in ganglia. That limitation has driven interest in gene-editing approaches that could directly destroy latent viral DNA. Researchers have developed a strategy using specialized enzymes delivered to nerve cells by viral vectors. In mouse models of both orofacial and genital HSV-1 infection, this approach eliminated 90% or more of latent viral DNA, and in some genital infection models reached 97%.30Nature Communications. Gene editing for latent herpes simplex virus infection reduces viral load and shedding in vivo CRISPR-based systems have also been explored for their ability to target and disrupt herpesvirus genomes during latency, with early lab work showing promise against HSV as well as related herpesviruses.31PubMed Central. Potential Application of the CRISPR/Cas9 System against Herpesvirus Infections
These results are encouraging but still years from human application. Delivering gene-editing tools to the right nerve cells in a living human brain and body without off-target effects is a formidable challenge. Still, for the first time, the idea of curing rather than simply suppressing herpes infection looks like a realistic goal for the next generation of antiviral research.
An Ancient Coevolutionary History
HSV-1 and HSV-2 have deep evolutionary roots that help explain their different tissue preferences and prevalence patterns. Phylogenetic analysis suggests HSV-1 codivergered with the human lineage over millions of years, making it one of our oldest persistent infections. HSV-2 took a different path: it appears to have jumped into an ancestor of modern humans from the ancestor of modern chimpanzees roughly 1.6 million years ago.32PubMed Central. Evolutionary origins of human herpes simplex viruses 1 and 2 That cross-species transmission event may explain why HSV-2 remains more narrowly adapted to genital tissue and the sacral ganglia, while HSV-1, with its far longer coevolutionary relationship with humans, has a broader repertoire of infection sites. Understanding this evolutionary context does not change how you manage a cold sore, but it does illuminate why these two closely related viruses behave so differently in the body and why HSV-1 is the dominant force in virtually every nongenital herpes condition.