Genital rash in women

A genital rash in women is any abnormal skin or mucosal change of the vulva, mons, groin, perineum or perianal skin, including erythema, papules, plaques, vesicles, erosions, ulcers, pustules, scale or pigment change. The most common causes are candidiasis, irritant and allergic dermatitis, intertrigo and inflammatory dermatoses (lichen sclerosus, lichen planus, psoriasis, lichen simplex).

The main clinical priorities are to separate infection from inflammatory dermatosis and to recognise sexually transmitted infection. Biopsy any lesion that persists or is atypical to exclude intraepithelial neoplasia and cancer.

Clinical relevance. Vulval disease is common and often mismanaged with repeated antifungal courses and unlabelled topical steroids. Lichen sclerosus and intraepithelial neoplasia carry a risk of squamous cancer, and syphilis, herpes and mpox have public health implications.

Anatomy. The keratinised vulval skin of the labia majora and mons is exposed to moisture and friction. The non keratinised labia minora and vestibule are thin, absorbent and sensitive to irritants. Hairbearing skin carries follicles and apocrine glands that can block and become infected.

Mechanisms. Rash results from infection (fungal, bacterial, viral, parasitic), irritation and allergy, autoimmune and immune mediated disease, neoplasia, drug reaction and systemic disease.

Classification.

• By morphology: erythematous, scaly, vesicular, erosive, ulcerative, papular or nodular, pustular, white, pigmented.
• By cause: infective, dermatitis, inflammatory dermatosis, bullous, drug related, neoplastic, systemic.

Key distinctions.

• Satellite pustules and itch suggest candidiasis.
• Vesicles and shallow erosions with pain suggest herpes.
• Shiny white atrophic skin with fissures and an hourglass shape around the vulva and anus suggests lichen sclerosus.
• Well defined red plaques in the groin skin folds with scale suggest tinea or psoriasis.
• Painless indurated ulcer suggests syphilis.
• Burrows and nocturnal itch suggest scabies.

History

• Onset, course, duration, itching, burning, pain, soreness, discharge, bleeding, dyspareunia, urinary symptoms, and effect on sleep and sex.
• Distribution: vulva only, groin folds, perianal, other body sites (scalp, elbows, nails, mouth).
• Prior episodes and response to treatment; antifungal courses and topical steroids already used.
• Sexual history, new partner, partner symptoms, contraceptive method, condom use, sexual practices.
• Skin and mucosal disease: eczema, psoriasis, lichen planus, oral ulcers, ocular symptoms, autoimmune disease, thyroid disease.
• Medical: diabetes, pregnancy, HIV, immunosuppression, anaemia, iron deficiency, incontinence, obesity.
• Drugs: new medicines in the past 2 weeks (co-trimoxazole, NSAIDs, tetracyclines, antibiotics, allopurinol, anticonvulsants), SGLT2 inhibitors (genital candidiasis).
• Irritant and allergen exposures: soaps, wipes, bubble baths, panty liners, perfumes, spermicides, lubricants, latex, topical anaesthetic, neomycin, depilation, tight clothing, urine or sweat exposure, dyes.
• Constitutional symptoms: fever, malaise, sore throat, lymphadenopathy, weight loss.
• Cancer risks: smoking, HPV, immunosuppression, lichen sclerosus.

Examination

• Vital signs and general skin examination, mouth, scalp, nails, lymph nodes.
• Inspect and photograph the vulva, groin, perianal area and thighs in good light.
• Describe distribution (symmetrical or not), morphology, colour, scale, fissures, erosions, ulcer depth, satellite lesions, loss of architecture (labial fusion, clitoral hood burying, introital narrowing), pigment change.
• Examine the vagina and cervix by speculum when tolerated (discharge, erosions, inflammation, strawberry cervix).
• Palpate groin nodes.
• Examine the partner when indicated.

Red flags

• Ulcer, plaque or erosion that persists for more than 4 weeks despite treatment.
• Pigmented lesion that is changing, irregular or larger than 6 mm.
• Raised, warty, fixed, bleeding or indurated lesion, or white thickened plaque (hyperkeratosis).
• Inguinal lymph node enlargement.
• Widespread blistering or skin pain with mucosal erosions, fever or a recent new medicine (Stevens Johnson syndrome, toxic epidermal necrolysis).
• Rapidly spreading erythema with severe pain, crepitus or systemic illness (necrotising infection).
• Genital ulcers in pregnancy near term or in an immunosuppressed woman.
• Fever with widespread vesicopustular rash (mpox, disseminated infection).
• Recurrent erosions in older women with lichen planus (scarring, squamous cancer risk).
• Suspected sexual abuse in a child.

Special groups. Pregnancy: herpes near term and candidiasis are common; many topical agents are safe but ivermectin, fluconazole and podophyllotoxin are avoided. Girls: streptococcal vulvitis, threadworm, lichen sclerosus, labial adhesions and abuse. Postmenopausal: atrophy, lichen sclerosus, vulval intraepithelial neoplasia and cancer. Immunosuppressed women: persistent herpes, warts, tinea and invasive fungal infection.

Organised by pattern of disease. Each cause is common unless marked serious or uncommon. Infective rashes

• Vulvovaginal candidiasis (erythema, oedema, fissures, white discharge, satellite pustules).
• Tinea cruris (annular edge, sparing of the labia minora).
• Erythrasma (Corynebacterium minutissimum, coral red fluorescence).
• Intertrigo with secondary candida or bacteria.
• Folliculitis, furunculosis, impetigo, bacterial vaginosis related irritation, trichomoniasis, streptococcal vulvovaginitis (children).
• Scabies, pediculosis pubis, threadworm (Enterobius vermicularis) with perianal itch, tungiasis.
• Genital herpes (herpes simplex virus 1 and 2), herpes zoster (sacral dermatome).
• Primary and secondary syphilis (chancre, condylomata lata, papular rash), chancroid, lymphogranuloma venereum, donovanosis.
• Genital warts, molluscum contagiosum.
• Mpox, hand foot and mouth disease (children).
• Staphylococcal scalded skin syndrome (children).

Dermatitis and eczema

• Irritant contact dermatitis (urine, faeces, sweat, wipes, soaps, panty liners, menstrual products).
• Allergic contact dermatitis (neomycin, benzocaine, preservatives, perfumes, latex, hair dye, spermicide).
• Atopic dermatitis, seborrhoeic dermatitis.
• Lichen simplex chronicus.
• Napkin dermatitis and incontinence associated dermatitis.
• Candidal intertrigo in diabetes and obesity.

Inflammatory dermatoses

• Lichen sclerosus (white, atrophic, fissured, sclerotic skin; itch; scarring; squamous cancer risk).
• Lichen planus (erosive vulvovaginal, Wickham striae, mouth involvement).
• Psoriasis (flexural, glazed red plaques without scale).
• Zoon (plasma cell) vulvitis.
• Hidradenitis suppurativa.
• Crohn disease (vulval oedema, ulcer, fissure).
• Hailey Hailey disease and Darier disease (uncommon).
• Aphthous ulcers and Behçet disease.

Bullous and drug related

• Fixed drug eruption (recurrent well defined erosions at the same site).
• Serious: Stevens Johnson syndrome and toxic epidermal necrolysis.
• Erythema multiforme (often herpes related).
• Pemphigus vulgaris, bullous pemphigoid, mucous membrane pemphigoid (scarring).
• Serious: graft versus host disease in transplant recipients.

Neoplasia and premalignancy

• Serious: vulval intraepithelial neoplasia (red, white or pigmented plaque).
• Serious: squamous cell carcinoma, melanoma, basal cell carcinoma, extramammary Paget disease (red eczematous plaque not responding to treatment).
• Cutaneous lymphoma and Langerhans cell histiocytosis (uncommon).

Systemic

• Zinc, biotin and iron deficiency.
• Kawasaki disease (perineal desquamation in children), scarlet fever, lupus, dermatomyositis.
• Pyoderma gangrenosum.
• Diabetes (recurrent candidiasis).

Stepwise reasoning

1. Describe the morphology and distribution, and ask about drugs, irritants and sexual risk.
2. Test for infection with swabs, scrapings and serology, and treat while waiting if symptoms are typical.
3. If the rash is persistent, atypical, fixed or has failed treatment after 4 weeks, biopsy it.
4. Test for diabetes and iron deficiency in recurrent disease.
5. Reconsider the diagnosis when treatment fails.

First line tests

• Vaginal pH (normal 3.8 to 4.5; over 4.5 in bacterial vaginosis and trichomoniasis; candidiasis usually has pH of 4.5 or less).
• Wet mount or Gram stain for pseudohyphae and yeast buds, clue cells and motile trichomonads; culture with species identification for recurrent infection (non albicans species are resistant to fluconazole).
• Nucleic acid amplification tests for chlamydia, gonorrhoea, Trichomonas vaginalis and Mycoplasma genitalium; HSV PCR from an unroofed vesicle or ulcer base; syphilis serology (treponemal enzyme immunoassay with RPR); HIV; hepatitis B and C.
• Skin scraping for potassium hydroxide microscopy and fungal culture (tinea); Wood lamp for coral red fluorescence of erythrasma.
• Dermoscopy and skin scrapings for scabies (burrows, delta wing sign, mites); inspection for lice and nits.
• Perianal tape test (adhesive tape in the early morning) for threadworm eggs.
• Mpox PCR from lesion swabs.
• Blood glucose or HbA1c, full blood count, ferritin, thyroid function in recurrent or chronic rash.
• Patch testing for suspected allergic contact dermatitis (after the rash settles).

Biopsy

• Punch biopsy (4 mm) under local anaesthetic (lidocaine 1% 2 to 5 mL; maximum 200 mg of plain lidocaine, 3 mg/kg) from the edge of an erosion or the thickest part of a plaque; two biopsies for blistering disease, including one perilesional sample for direct immunofluorescence.
• Indications: lesion persisting after 4 weeks of treatment, pigment change, ulcer, warty or fixed lesion, white thickened plaque, suspected pemphigoid or pemphigus, suspected lichen planus or lichen sclerosus when diagnosis is unclear, atypical response, and any lesion in a woman with lichen sclerosus that changes.

Limitations. Many vulval conditions overlap, so mixed diagnoses occur. Culture and microscopy have limited sensitivity. Topical steroids and antifungals can modify the appearance and lower diagnostic yield. Biopsy of a large erosion may show only non specific inflammation, so repeat from the edge when suspicion remains.

Immediate steps. Stop all potential irritants and unnecessary topical products. Admit women with suspected Stevens Johnson syndrome, toxic epidermal necrolysis, necrotising infection, or generalised herpes. Provide analgesia and sitz baths. Test and treat for sexually transmitted infection when risk is present, and tell partners.

General measures. Wash with water or an emollient soap substitute only. Use emollient such as white soft paraffin or liquid paraffin twice daily, and as a barrier before urine or sweat exposure. Wear loose cotton underwear, avoid wipes, perfumes, panty liners, depilation and tight clothing. Treat incontinence and constipation. Control diabetes.

Analgesia. Paracetamol 1 g orally every 4 to 6 hours, maximum 4 g daily (3 g daily with chronic alcohol use, malnutrition or hepatic impairment; 15 mg/kg each dose under 50 kg). Lidocaine 5% ointment to the area for short term relief (maximum 20 g daily; avoid sensitisation by limiting duration and watch for contact allergy).

Vulvovaginal candidiasis

• Fluconazole 150 mg orally as a single dose; for severe disease or immune suppression repeat once after 72 hours. Contraindicated in pregnancy; interacts with warfarin, statins, ciclosporin, phenytoin and QT prolonging drugs; a single dose needs no adjustment, and repeated doses are halved when creatinine clearance is 50 mL/min or less.
• Clotrimazole 500 mg pessary inserted once, with clotrimazole 1% cream applied externally two to three times daily for 7 days, or clotrimazole 2% cream twice daily for 7 days.
• Pregnancy: clotrimazole 100 mg pessary at night for 7 days, with topical cream.
• Recurrent infection (4 or more episodes in 12 months): confirm by culture, then fluconazole 150 mg orally on days 1, 4 and 7, followed by 150 mg once weekly for 6 months. Review glucose control and SGLT2 inhibitor use. Non albicans species: boric acid 600 mg vaginal capsule nightly for 14 days or flucytosine specialist regimen.

Contact dermatitis (irritant and allergic)

• Remove the cause and apply emollient.
• Hydrocortisone 1% ointment once or twice daily for 1 to 2 weeks (mild); if there is no response, clobetasone butyrate 0.05% ointment once daily for up to 7 days (moderately potent, specialist review); patch test for persistent disease.
• Sedating antihistamine at night: hydroxyzine 10 to 25 mg orally (maximum 100 mg daily; avoid in older adults, QT prolongation, pregnancy).

Seborrhoeic dermatitis, psoriasis, atopic dermatitis

• Emollients and gentle cleansing.
• Seborrhoeic: ketoconazole 2% cream twice daily for 2 to 4 weeks with hydrocortisone 1% ointment once daily for up to 7 days.
• Flexural psoriasis: hydrocortisone 1% or clobetasone butyrate 0.05% ointment once daily for up to 2 weeks, then tacrolimus 0.1% ointment twice daily (off label, specialist, avoid in immunosuppression). Avoid calcipotriol on genital skin because of irritation.
• Atopic: emollients with low or moderate potency steroid for flares, and tacrolimus 0.03% ointment twice daily as a maintenance option.

Lichen simplex chronicus. Break the itch scratch cycle: clobetasol propionate 0.05% ointment 0.5 g nightly for 4 weeks, then alternate nights for 4 weeks, then twice weekly for 4 weeks. Amitriptyline 10 mg orally at night, increased by 10 mg every 1 to 2 weeks to 50 to 75 mg at night (maximum 100 mg), to reduce nocturnal scratching; ECG when over 50 years or with heart disease.

Cut nails, and use cold compresses.

Lichen sclerosus. Clobetasol propionate 0.05% ointment 0.5 g nightly for 4 weeks, then alternate nights for 4 weeks, then twice weekly for 4 weeks, then the minimum needed (usually 1 to 2 times weekly or when symptomatic) for life. Continue emollients. Review at 3 months and then every 6 to 12 months for scarring and early neoplasia. Biopsy any new nodule, ulcer or non responding area.

Surgery for scarring (labial fusion, phimosis of the clitoral hood) after control of inflammation.

Lichen planus (erosive). Clobetasol propionate 0.05% ointment 0.5 g nightly for 4 weeks, then reduce, with hydrocortisone 10% foam or suppositories intravaginally (specialist) to prevent adhesions; dilators; treatment of mouth disease. Second line (specialist): tacrolimus 0.1% ointment twice daily, methotrexate 7.5 to 15 mg orally once weekly with folic acid 5 mg weekly (not in pregnancy; monitor full blood count and liver function), hydroxychloroquine 200 to 400 mg daily, mycophenolate. Lifelong follow up for neoplasia.

Tinea cruris. Terbinafine 1% cream once or twice daily for 1 to 2 weeks, or clotrimazole 1% cream twice daily for 2 to 4 weeks; extensive disease: terbinafine 250 mg orally once daily for 2 weeks (avoid in liver disease and creatinine clearance under 50 mL/min; check liver function for longer courses). Reduce moisture.

Erythrasma. Topical clindamycin 1% lotion twice daily for 2 weeks, or erythromycin 500 mg orally four times daily for 14 days, or clarithromycin 1 g orally as a single dose.

Bacterial rashes. Localised impetigo or folliculitis: hydrogen peroxide 1% cream three times daily for 5 days, or mupirocin 2% ointment three times daily for 5 days (maximum 10 days). Extensive or cellulitic: flucloxacillin 500 mg orally four times daily for 5 to 7 days (maximum 4 g daily; penicillin allergy: clarithromycin 500 mg twice daily). Streptococcal vulvitis in girls: phenoxymethylpenicillin 250 mg to 500 mg orally four times daily for 10 days (dose by weight in children).

Scabies. Permethrin 5% cream applied to the whole body from the neck to the soles (including the genital area, folds, under nails) and washed off after 8 to 12 hours, repeated after 7 days. Alternative: ivermectin 200 microgram/kg orally with food as a single dose, repeated after 7 to 14 days (not in pregnancy or in children under 15 kg).

Treat all household and sexual contacts at the same time, and wash clothes and bedding at 50 degrees or more.

Itch can persist for 4 weeks after cure; crotamiton or low potency steroid and antihistamines help.

Pediculosis pubis. Permethrin 5% cream applied to the genital area, thighs and trunk, left for 8 to 12 hours, repeated after 7 days, or malathion 0.5% aqueous lotion left for 12 hours and repeated after 7 days. Remove nits, wash clothes and bedding, treat partners, and test for other sexually transmitted infections.

Threadworm. Mebendazole 100 mg orally as a single dose, repeated after 2 weeks (treat the whole household; not under 6 months of age, and avoided in the first trimester), with hygiene measures.

Genital herpes. First episode: aciclovir 400 mg orally three times daily for 5 days (extended to 7 to 10 days if new lesions continue; adjust to creatinine clearance under 25 mL/min). Alternatively, valaciclovir 500 mg orally twice daily for 5 days.

Recurrent episode: aciclovir 800 mg orally three times daily for 2 days, or valaciclovir 500 mg orally twice daily for 3 days.

Suppression: aciclovir 400 mg orally twice daily, or valaciclovir 500 mg orally once daily, for 6 to 12 months, then review. Topical lidocaine 5% ointment, saline baths and analgesia.

Pregnancy: aciclovir from the first presentation, and suppressive aciclovir 400 mg three times daily from 36 weeks of gestation; plan caesarean section with a primary episode in the third trimester.

Syphilis. Primary, secondary or early latent: benzathine benzylpenicillin 2.4 million units intramuscularly once (second dose after 1 week in pregnancy); doxycycline 100 mg orally twice daily for 14 days if allergic and not pregnant. Late latent: benzathine benzylpenicillin 2.4 million units intramuscularly weekly for 3 weeks. Warn about the Jarisch Herxheimer reaction; follow serology at 3, 6 and 12 months; treat partners; test for HIV.

Mpox. Supportive care, analgesia, wound care and isolation until all lesions have crusted and fresh skin has formed. Specific antiviral therapy (tecovirimat) is for severe disease or immunosuppression in specialist or research settings, because randomised studies have not shown clear benefit.

Vaccination for contacts and high risk groups. Notify as local rules require.

Warts and molluscum. Cryotherapy or trichloroacetic acid 80 to 90% weekly for up to 6 weeks; podophyllotoxin 0.5% solution twice daily for 3 days then stopped for 4 days for up to 4 cycles (external only, not in pregnancy); imiquimod 5% cream 3 times weekly for up to 16 weeks and washed off after 6 to 10 hours. Offer HPV vaccination.

Fixed drug eruption. Stop the culprit drug (commonly co-trimoxazole, NSAIDs, tetracyclines), apply clobetasol propionate 0.05% ointment 0.5 g once daily for 7 days, and give an allergy record.

Stevens Johnson syndrome and toxic epidermal necrolysis. Stop all suspected drugs immediately. Admit to a burns or intensive care unit for fluids, nutrition, pain control, eye and mucosal care, and infection surveillance. Immunomodulating therapy (ciclosporin 3 to 5 mg/kg orally daily in divided doses for 7 to 10 days, or high dose intravenous immunoglobulin) is specialist treatment, with limited evidence.

Bullous diseases. Specialist dermatology and gynaecology review; prednisolone 0.5 to 1 mg/kg orally daily for pemphigus and pemphigoid with steroid sparing agents, potent topical steroid for localised disease, and bone, glucose and infection prophylaxis.

Premalignant and malignant disease. Biopsy, then excision, ablation or topical therapy (imiquimod 5% cream) for vulval intraepithelial neoplasia; wide local excision for Paget disease; and cancer care for invasive disease.

Special groups. Pregnancy: use emollients, topical clotrimazole, topical steroids and acyclovir where indicated; avoid fluconazole, ivermectin, podophyllotoxin, imiquimod and methotrexate. Girls: emollients, barrier creams and hygiene; streptococcal vulvitis treated with antibiotics; threadworm treated for the household; refer for lichen sclerosus. Older women: vaginal oestrogen (oestradiol 10 microgram vaginal tablet nightly for 2 weeks, then twice weekly) when atrophy contributes.

Monitoring. Review at 2 to 4 weeks for response (earlier for blisters or suspected severe reaction). Review chronic dermatoses every 3 to 6 months, then yearly. Count steroid use in grams. Repeat serology for syphilis at 3, 6 and 12 months. Follow up biopsy results within 2 weeks.

Referral and escalation. Refer urgently within 2 weeks for suspected cancer. Refer to gynaecology or dermatology for lichen sclerosus, lichen planus, bullous disease, vulval intraepithelial neoplasia, refractory vulvovaginitis and diagnostic uncertainty. Refer to genitourinary medicine for sexually transmitted infection. Refer to paediatrics for a rash in a girl with suspected abuse, and to infectious diseases for mpox or disseminated infection.

Admission criteria. Suspected Stevens Johnson syndrome or toxic epidermal necrolysis, necrotising infection, disseminated herpes or primary herpes with urinary retention, severe pain not controlled by oral analgesia, systemic illness, and immunosuppressed women with extensive disease.

Discharge and follow up. Most women are outpatients. Give written instructions on emollients, topical steroid amounts (one fingertip unit is about 0.5 g) and avoidance of irritants.

Safety netting. Return for spreading redness, fever, blistering, a sore that does not heal in 4 weeks, bleeding, a new lump, urinary retention, severe pain or worsening symptoms.