Sexually Transmitted Skin Infections

Sexually Transmitted Infections:

• Sexually transmitted infections (STIs) are infections that can spread through vaginal, anal or oral sexual contact. Some can also spread through close skin-to-skin contact, blood exposure, or from a pregnant person to the baby.
• This page focuses on common conditions that frequently bring patients to a dermatologist or sexual-health clinic: genital warts, genital molluscum contagiosum, syphilis and genital herpes.
• They are very different infections. Genital warts and molluscum are usually visible skin lesions; syphilis can affect the whole body; herpes typically causes painful blisters or ulcers.
• Not every genital lesion is an STI. Skin tags, folliculitis, cysts, dermatitis,fungal infections and other conditions can look surprisingly similar.
• The good news: these conditions are manageable. Some can be cured, while others can be controlled very effectively.

How Common Are These Infections?

• HPV: Human papillomavirus is the most common STI worldwide. Low-risk HPV types, especially 6 and 11, cause about 90% of anogenital warts.
• India: An estimated genital-wart prevalence of about 1.07% in India, with higher reported prevalence in men and substantial regional variation.
• Molluscum: Molluscum contagiosum is common in children, but in adults, genital lesions are an important sexually associated presentation. It is also more extensive and persistent in people with impaired immunity.
• Syphilis: Syphilis remains a major global STI. It can move through primary, secondary, latent and late stages, and untreated disease may involve the nervous system, eyes, heart or blood vessels.
• Herpes: HSV-1 and HSV-2 are extremely common worldwide. Genital infection can be caused by either type; HSV-1 is now responsible for a substantial share of new genital herpes infections in many settings.

1. Genital Warts (Hpv)

What are genital warts?

• Genital warts, also called anogenital warts or condyloma acuminata, are benign growths caused mainly by low-risk HPV types 6 and 11.
• They may appear as tiny smooth bumps, flat papules, finger-like growths or classic cauliflower-like lesions.
• They can occur on the penis, scrotum, vulva, vaginal opening, perineum, around the anus and, less commonly, inside the anal canal, vagina, cervix or urethra.
• A person may have only one or two lesions or many lesions that merge together.

How does HPV spread?

• Main route: intimate skin-to-skin sexual contact.
• Penetrative sex is not required; genital-to-genital, oral-genital and close sexual skin contact can transmit HPV.
• Condoms reduce exposure but cannot cover every area of skin, so they lower risk rather than eliminate it.
• HPV can be acquired from a partner who has no visible wart because viral shedding may occur without obvious lesions.
• A wart appearing months after sexual contact does not prove recent transmission or infidelity. HPV can remain unnoticed for a long time.

Why do some people develop warts while others do not?

• Intrinsic factors: age, immune response, genetic susceptibility, pregnancy-related immune changes and immunosuppression.
• Extrinsic factors: new or multiple sexual partners, close skin-to-skin sexual exposure, smoking and repeated exposure to HPV.
• Immunosuppression: warts may be larger, more numerous, more persistent and harder to treat in people with HIV or other causes of reduced immunity.

What happens inside the skin? — Pathophysiology

• HPV enters through tiny breaks or vulnerable areas of the epithelium.
• The virus infects basal keratinocytes and uses the normal maturation of skin cells to reproduce.
• Viral proteins alter cell growth and differentiation, producing the visible wart.
• Low-risk HPV types 6 and 11 usually produce benign warts rather than cancer.
• The immune system often suppresses HPV over time, but treatment of a visible wart does not necessarily mean every HPV-infected cell has immediately disappeared. This explains recurrence.

How are genital warts diagnosed?

• Usually by clinical examination. An experienced dermatologist can often diagnose them from their shape and distribution.
• Dermoscopy can sometimes help when the diagnosis is uncertain.
• Biopsy is appropriate when a lesion is atypical, pigmented, ulcerated, indurated, bleeding, rapidly changing, unusually resistant to treatment or when cancer cannot be excluded.
• Routine HPV typing is not usually needed just to diagnose an external genital wart.
• If genital warts are diagnosed, the clinician may offer testing for other STIs based on symptoms and sexual history.

Treatment of genital warts

Medical / topical options

• Imiquimod cream: Stimulates local immune responses in external genital warts. It is patient-applied and can cause redness, burning or irritation.
• Podophyllin: A doctor-applied treatment for selected genital warts. It must be used carefully and is not appropriate during pregnancy.
• Trichloroacetic acid (TCA): A clinician-applied chemical treatment, useful for smaller moist lesions and mucosal sites.
• Other specialist options: Selected cases may require combination or alternating topical destructiveand immune-modulating approaches depending on site, recurrence and immune status.

Procedural options

• Cryotherapy: Freezes the wart. It works well for small and multiple lesions, but several sessions may be needed.
• Electrocautery / electrosurgery: Uses controlled heat to destroy the warts.
• Laser treatment: A precise option for selected extensive, thick or difficult-to-treat lesions.
• Surgical removal: For large or pedunculated lesions and allows tissue to be sent for histopathology.

HPV vaccination

• HPV vaccination is one of the most important ways to prevent HPV-related disease.
• The vaccine is preventive: it works best before exposure to HPV, but vaccination may still offer protection against HPV types to which a person has not yet been exposed.
• Vaccination does not treat an existing wart.
• Evidence that HPV vaccination prevents recurrence of already treated genital warts is still limited and mixed; therefore it should not be promised as a “prevention of recurrence” treatment.
• Vaccination decisions should be based on patient's age, previous vaccination, sex, immune status and lifestyle.

Prognosis of genital warts

• Genital warts are benign and are not the same thing as genital cancer.
• Some disappear without treatment as the immune system controls HPV; others persist or increase in number.
• Recurrence after treatment is common, particularly during the first few months, because treatment removes visible lesions but may not immediately eliminate HPV from surrounding skin.
• A recurrence does not automatically mean treatment failure or a new sexual exposure.
• Persistent, atypical or treatment-resistant lesions deserve reassessment and sometimes biopsy.

2. Genital Molluscum Contagiosum

What is genital molluscum?

• Molluscum contagiosum is caused by molluscum contagiosum virus, a poxvirus.
• The classic lesion is a small, smooth, pearly or skin-coloured bump with a central dimple (umbilication).
• In adults, lesions around the genitals, pubic area, lower abdomen or inner thighs may be sexually transmitted
• In children, molluscum is usually spread by close contact rather than sexual transmission.
• Risk factors and transmission
• Intrinsic factors: young age, eczema/skin-barrier problems and reduced immunity.
• Extrinsic factors: close skin contact, sexual contact in adults, sharing personal items, and scratching or shaving that spreads lesions to nearby skin.
• Auto-inoculation is common: touching or scratching one lesion can help spread the virus to another area.
• Extensive facial or genital molluscum in an adult, especially with large or persistent lesions, should prompt consideration of an underlying immune problem.

Pathophysiology

• The virus enters superficial skin through small breaks in the epidermis.
• Viral replication enlarges keratinocytes containing viral inclusion bodies.
• The central dimple contains viral material and explains why squeezing lesions is a poor idea: it can spread infection and cause inflammation or scarring.

Diagnosis

• Usually clinical: smooth, firm, dome-shaped papules with central umbilication.
• Dermoscopy can help when lesions are small or atypical.
• Biopsy is rarely needed but may be considered for unusual, giant, inflamed or doubtful lesions.
• Adults with genital molluscum should be offered appropriate STI screening based on risk and clinical assessment.

Treatment options

• Observation: Reasonable for selected immunocompetent patients with few, asymptomatic lesions. Spontaneous clearance can occur, but the time course is unpredictable.
• Cryotherapy: A practical clinic-based treatment.
• Curettage: Direct physical removalcan provide rapid clearance.
• Electrocautery: Useful for selected lesions, especially when a rapid procedural approach is preferred.
• Topical treatments: Potassium hydroxide is sometimes used in children. Treatment should be selected according to age, site and severity.

Prognosis

• Molluscum is usually benign and eventually clears in immunocompetent people.
• Individual lesions may persist for months; some cases last considerably longer.
• Scratching can cause bacterial infection, eczema-like inflammation and spread to new sites.
• Genital lesions are often treated because of transmission concerns, cosmetic impact and the risk of spreading lesions to nearby skin.

3. Syphilis

What is syphilis?

• Syphilis is a bacterial STI caused by Treponema pallidum.
• It can affect the skin, mucous membranes, lymph nodes, nervous system, eyes and cardiovascular system.
• It is sometimes called 'the great imitator' because its skin findings can resemble many other diseases.
• Syphilis can be cured with appropriate antibiotics, but damage caused by late untreated infection may not always be reversible.

How is syphilis spread?

• Most commonly through sexual contact with an infectious lesion during physical contact.
• It can also pass from a pregnant person to the foetus, causing congenital syphilis.
• Transmission risk is highest when infectious lesions are present, particularly during early disease.
• A person may have syphilis without obvious symptoms.

Risk factors and contributing factors

• Intrinsic: immune status, pregnancy and coexisting HIV infection can influence presentation and complications.
• Extrinsic: exposure to an infected partner, multiple/new partners, inconsistent barrier use and limited access to testing or treatment.
• Social factors such as stigma, delayed testing, poor access to healthcare and missed partner treatment can allow transmission to continue.

Pathophysiology — why syphilis can affect the whole body

• Treponema pallidum enters through mucosal or skin breaks and disseminates through the bloodstream and lymphatic system.
• The primary stage produces a chancre(ulcer-raw area) at the entry site.
• Secondary disease reflects systemic spread and immune response, often producing a widespread rash and mucosal lesions.
• The organism may then enter a latent phase with no symptoms.
• Untreated infection can later involve the nervous system, eyes and cardiovascular system.

The stages of syphilis — in simple terms

Investigations for suspected syphilis

• Nontreponemal test: VDRL or RPR. Useful for screening and for following treatment response because titres generally fall after successful treatment.
• Treponemal test: TPHA/TPPA, treponemal EIA/CLIA or related assays. These help confirm exposure/infection but often remain positive for life.
• Two-test interpretation: A diagnosis should not be made from a single reactive test without considering the clinical picture and the testing algorithm.

Treatment of syphilis

• First-line therapy: Long-acting benzathine penicillin G remains the standard treatment for uncomplicated syphilis, with the number of doses determined by stage and clinical situation.
• Early syphilis: A single intramuscular dose of benzathine penicillin G 2.4 million units is the standard regimen for primary, secondary and early latent disease in adults in major guidelines.
• Late latent or unknown duration: Three weekly doses of benzathine penicillin G 2.4 million units are generally recommended, for a total of 7.2 million units.
• Penicillin allergy: Alternative treatment may be considered in selected non-pregnant adults, but pregnancy requires special handling; penicillin is the treatment of choice in pregnancy.
• Jarisch–Herxheimer reaction: Fever, chills, headache or worsening symptoms can occur shortly after treatment because of an inflammatory response. It is not the same as a penicillin allergy.

Follow-up after syphilis treatment

• Follow-up uses quantitative RPR or VDRL titres at recommended intervals to assess response.
• A fall in titre is expected after effective treatment, but the speed and degree of decline vary with stage and baseline titre.
• Persistent low-level reactivity can occur ('serofast' state) and does not automatically mean active untreated infection.
• A new rise in titre, new symptoms or a compatible exposure may indicate reinfection or treatment failure and requires reassessment.
• Sexual partners who may have been exposed should be evaluated according to the stage and timing of the infection.

Prognosis

• Syphilis is curable when diagnosed and treated appropriately.
• Early treatment prevents most long-term complications.
• Untreated infection can persist for years and can cause serious neurologic, ocular and cardiovascular disease.
• A person can be infected again after successful treatment. Treatment does not create lifelong immunity.

Latest advances in syphilis

• Doxycycline post-exposure prophylaxis (doxy-PEP) has emerged as a prevention strategy for selected high-risk populations and has shown substantial reductions in syphilis and chlamydia in trials. It is not a replacement for diagnosis, condoms, testing or treatment.

4. Genital Herpes (Herpes Genitalis)

What is genital herpes?

• Genital herpes is caused by herpes simplex virus type 1 (HSV-1), type 2 (HSV-2), or occasionally both.
• HSV-2 has traditionally been the major cause of recurrent genital herpes, but HSV-1 now causes many new genital infections.
• The virus stays in the body after the first infection and can reactivate later.
• Some people have obvious painful outbreaks; others have mild symptoms or no recognized symptoms at all.

How is herpes spread?

• Through direct skin or mucosal contact with an infected area.
• Transmission can occur during visible blisters/ulcers and also during asymptomatic viral shedding.
• Condoms reduce but do not completely eliminate transmission because infected skin may lie outside the covered area.
• Genital HSV-1 is often acquired through oral-genital contact.
• A person can have herpes without knowing who transmitted it or when the infection was acquired.

Intrinsic and extrinsic factors

• Intrinsic: immune response, previous HSV exposure, pregnancy and immune suppression can influence severity and recurrence.
• Extrinsic triggers: illness, stress, friction, sleep deprivation and other individual triggers may precede recurrences, although triggers vary widely.
• HSV-2 generally recurs and sheds more often from the genital tract than genital HSV-1.

Pathophysiology — why herpes comes back

• HSV first infects epithelial cells and multiplies locally, producing blisters, erosions or ulcers.
• The virus then travels along sensory nerves and establishes lifelong latency in sensory ganglia.
• Later, reactivation can send virus back down the nerve to the skin or mucosa.
• The immune system controls the infection but does not normally remove latent HSV from the body.
• This explains why antiviral treatment controls outbreaks and shedding but does not currently eradicate the latent virus.

Typical symptoms

• Painful grouped blisters that break into shallow ulcers.
• Burning, tingling or itching before lesions appear.
• Pain during urination if lesions involve the urethral opening or nearby skin.
• Tender groin lymph nodes and flu-like symptoms can occur with a first episode.
• Some people have tiny fissures or mild redness rather than classic blisters, making clinical diagnosis difficult.

How is genital herpes diagnosed?

• Best test when a lesion is present: HSV PCR/NAAT from a fresh lesion is highly sensitive and can identify HSV-1 versus HSV-2. Availability is poor.
• Viral culture: Can be used but is less sensitive, especially when lesions are healing.
• Type-specific blood tests: May help in selected situations, such as recurrent or atypical symptoms with no lesion available, but results must be interpreted carefully.
• What not to do: Routine HSV blood screening of people without symptoms is not recommended in many settings because false positives and uncertain interpretation can cause significant anxiety.

Treatment of genital herpes

• First clinical episode: Oral antiviral therapy should be started promptly.
• Recurrent herpes: Short courses of oral antiviral therapy work best when started very early, ideally during tingling/burning or within the first day of lesions.
• Suppressive therapy: Daily antiviral therapy can reduce recurrence frequency and reduce HSV-2 transmission risk in discordant couples when used appropriately.
• Pain control: Simple analgesics, gentle cleansing and keeping the area dry can make an outbreak easier to tolerate.

Pregnancy and herpes

• Genital herpes needs special attention during pregnancy because transmission to a newborn can occur.
• The risk is particularly important when a pregnant person acquires a new genital HSV infection near delivery.
• Pregnant patients with genital herpes or a partner with known HSV should discuss the situation early with their obstetrician/dermatologist.
• Antiviral therapy and delivery planning are individualised according to the clinical history and timing of infection.

Prognosis

• Genital herpes is lifelong, but for most people it is manageable.
• Recurrences usually become less frequent or less severe over time, although the pattern varies.
• Genital HSV-1 tends to recur and shed less frequently than genital HSV-2.
• The diagnosis can cause disproportionate fear and relationship stress. Good counselling is part of treatment.

A Practical STI Assessment at a Dermatology Clinic

• A confidential history covers symptoms, timing, recent exposures, previous STIs, contraception/barrier use, pregnancy possibility and relevant medical conditions.
• The pattern, location and appearance of a lesion often provide the first major clue.
• Not every patient needs every STI test; the panel should match symptoms, exposures, local prevalence and clinical risk.
• Treat the diagnosed infection — not just the visible symptom. For example, removing a wart is not the same as eradicating HPV, and treating a herpes ulcer with an antibiotic will not treat HSV.
• Address partners. Some infections require partner notification, testing or treatment.
• Plan follow-up. Syphilis requires serologic follow-up; recurrent herpes may need episodic or suppressive treatment; recurrent warts may need another treatment approach.
• Talk about prevention. Vaccination, barrier methods, testing, partner communication and avoiding physical contact during active lesions can reduce risk.

When Should You See a Dermatologist or STI Specialist?

• A new genital lump, wart, blister, ulcer or unexplained rash.
• A painless genital ulcer — especially because primary syphilis can be painless.
• Painful blisters or ulcers that recur.
• Genital lesions that bleed, become hard, change colour or do not heal.
• Multiple or rapidly increasing lesions.
• A positive VDRL/RPR, TPHA/TPPA or HSV test that you are unsure how to interpret.
• A suspected STI during pregnancy.
• A partner has been diagnosed with an STI.
• Persistent or unusually extensive molluscum or warts.

What Patients Should NOT Do

• Do not burn genital lesions with acids, household chemicals or unprescribed wart removers.
• Do not squeeze or repeatedly shave over molluscum lesions.
• Do not take antibiotics 'just in case'. The wrong antibiotic can delay diagnosis and contribute to resistance.
• Do not assume that a normal-looking genital area means there is no STI; some infections are asymptomatic.
• Do not assume a positive test automatically tells you when or from whom you acquired an infection.
• Do not stop syphilis treatment or follow-up simply because the rash or ulcer has disappeared.
• Do not rely on internet photographs for diagnosis. Several non-STI skin conditions look almost identical to common STIs.

Prevention: What Actually Helps?

• HPV vaccination: The strongest prevention tool for HPV-related disease.
• Condoms: Reduce exposure and are especially useful when used consistently, but they do not cover all potentially infected skin.
• Testing: Regular STI screening based on sexual health risk can find infections before complications or onward transmission.
• Avoid sex during active lesions:
• Partner communication:
• Do not share needles or blood-contaminated equipment: Relevant for blood-borne infections such as HIV and hepatitis.
• Complete treatment and follow-up: Treating the infection is not enough if partners remain untreated or follow-up is missed.

The Bottom Line

• Genital warts, molluscum, syphilis and herpes are different diseases and need different treatments.
• A genital lesion is not automatically an STI — but a new lesion should not be ignored.
• Many STIs are treatable or very effectively controllable.
• Early diagnosis reduces complications, anxiety and transmission.
• For recurrent or persistent lesions, a dermatologist can often provide both diagnosis and procedural treatment.
• Confidentiality, clear explanation and a non-judgemental approach are as important as the medicine itself.

Frequently Asked Questions