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OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Vulvovaginal candidiasis and bacterial vaginosis

Obstetrics and gynaecology · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Vaginitis should not explain systemic illness

Severe pelvic pain, fever, haemodynamic change, peritonism, rapidly spreading vulval inflammation or pregnancy with pain and bleeding is not uncomplicated candidiasis or bacterial vaginosis.

Action: Assess observations and pregnancy status, examine for upper-tract or invasive infection, and arrange same-day acute care rather than repeatedly treating a presumed lower-vaginal condition.

Overview

Diagnose and manage candidiasis and bacterial vaginosis accurately, including pregnancy, recurrence, non-albicans yeast, medicine safety and appropriate avoidance of unnecessary partner treatment.

Candidiasis and bacterial vaginosis are common but biologically different. Vulvovaginal candidiasis is symptomatic inflammation associated with Candida, most often C. albicans. Bacterial vaginosis is a shift from lactobacillus dominance toward a diverse anaerobic biofilm and usually produces little inflammation. Both can recur, coexist with sexually transmitted infection and be overdiagnosed from discharge appearance. Ask about the dominant symptom, episode pattern, self-treatment, pregnancy, diabetes, immunosuppression, recent antibiotics and exposure to irritants.

Candidiasis is supported by itch, burning, vulval soreness, erythema, oedema, fissures and compatible yeast on microscopy or culture. Discharge is variable; the absence of a curdy appearance does not exclude it. A normal acidic pH helps distinguish Candida from bacterial vaginosis or trichomoniasis. In a first typical mild episode, clinical diagnosis may be reasonable, but microscopy and culture become important for severe, recurrent or persistent symptoms, possible non-albicans infection and treatment failure. A positive culture without symptoms is colonisation and should not trigger therapy.

Aetiology

01

Candida-associated inflammation

Usually C. albicans transitions from colonisation to symptomatic mucosal inflammation, facilitated by antibiotics, pregnancy, diabetes, immunosuppression or host susceptibility.

02

Anaerobic vaginal dysbiosis

Bacterial vaginosis reflects loss of lactobacillus dominance and expansion of mixed anaerobes within an adherent biofilm rather than invasion by one pathogen.

03

Recurrence modifiers

Persistent biofilm, host response, repeated antimicrobial exposure, sexual networks and unrecognised alternative diagnoses contribute differently to recurrent symptoms.

Pathophysiology

  1. 1
    Yeast-driven inflammation

    Candida adherence and filamentation provoke epithelial and neutrophil responses, producing intense itch, burning, erythema and fissuring despite superficial infection.

  2. 2
    Acidity is preserved

    Candida disease usually occurs without the lactobacillus depletion that raises pH, so vaginal acidity commonly remains at 4.5 or below.

  3. 3
    Biofilm alters flora

    BV-associated organisms form a polymicrobial biofilm, generate amines and reduce protective lactobacilli, causing odour and homogeneous discharge with limited inflammation.

  4. 4
    Recurrence follows persistence

    Incomplete ecological recovery or persistent yeast susceptibility can allow symptoms to return after apparently adequate short treatment despite initial clinical improvement.

Clinical features and red flags

Typical candidiasis

Prominent itch or soreness with erythema, oedema, fissures and non-offensive discharge, usually at pH 4.5 or below, supports symptomatic Candida inflammation.

Typical bacterial vaginosis

Thin homogeneous discharge, characteristic odour, minimal inflammation, clue cells and pH above 4.5 form a coherent bacterial-vaginosis phenotype.

Recurrent candidiasis

Four or more symptomatic episodes within twelve months require confirmation, species identification and assessment for modifiers before prolonged suppressive treatment.

Discordant inflammation

Severe pain, ulceration, cervical tenderness, marked vulvitis or systemic illness is discordant with uncomplicated bacterial vaginosis and broadens the differential.

Red flags requiring action

  • Lower abdominal pain, fever, cervical excitation or adnexal tenderness requires assessment for pelvic inflammatory disease and other pelvic emergencies.
  • Pregnancy with pain, bleeding, collapse or shoulder-tip pain requires urgent ectopic-pregnancy assessment regardless of discharge symptoms.
  • Extensive oedema, ulceration, necrosis, urinary retention or rapidly spreading erythema suggests severe infection or an alternative vulval disorder.
  • Persistent postcoital, intermenstrual or postmenopausal bleeding should not be attributed to vaginitis without cervical and cancer-focused assessment.

Investigations

  1. 01
    Vaginal pH and bedside microscopyFirst step
    Why
    Support rapid differentiation of acidic Candida-associated inflammation from dysbiosis or trichomoniasis.
    Interpretation and limitations
    Budding yeast or pseudohyphae with symptoms supports candidiasis; clue cells and pH above 4.5 support bacterial vaginosis, but a negative wet mount is not fully sensitive.
  2. 02
    High vaginal swab for fungal culture
    Why
    Confirm recurrent, complicated or treatment-resistant candidiasis and identify the Candida species.
    Interpretation and limitations
    Growth is meaningful only with compatible symptoms; non-albicans isolation requires clinical correlation because colonisation is common and standard fluconazole response may be poor.
  3. 03
    Gram stain or validated BV assay
    Why
    Provide laboratory confirmation when Amsel testing is incomplete, recurrence is frequent or the diagnosis is uncertain.
    Interpretation and limitations
    A flora pattern consistent with BV supports treatment in a symptomatic person; molecular detection of associated bacteria does not by itself establish symptomatic disease.
  4. 04
    Pregnancy testing and targeted STI NAAT
    Why
    Guide medicine safety and detect coexisting cervical or protozoal infection according to exposure.
    Interpretation and limitations

Differential diagnosis

01

Trichomoniasis

Raised pH, inflammation and malodorous discharge can mimic BV, but validated organism testing creates partner-treatment and abstinence requirements.

02

Contact dermatitis

Soaps, wipes, pads and topical self-treatment cause itch, burning and erythema without yeast, often worsening after repeated products.

03

Vulval dermatosis

Lichen sclerosus, eczema and lichen planus produce persistent itch, fissures, architectural or colour change and require inspection and targeted specialist care.

04

Genitourinary syndrome

Oestrogen deficiency causes dryness, burning, dyspareunia, urinary symptoms and fragile pale tissue, sometimes with secondary discharge or raised pH.

05

Cervical infection

Chlamydia and gonorrhoea may cause mucopurulent discharge or contact bleeding, which vaginal antifungal and BV regimens do not treat.

Additional chapter-specific clues

Mixed or alternative disease

Raised pH plus inflammation may indicate trichomoniasis or mixed infection, while repeated negative microscopy suggests dermatitis, dermatosis or vulvodynia.

Management

01Initial episodeConfirm the dominant syndromeFirst stepA stable patient presents with new vulvovaginal symptoms and no major recurrence history.+
  1. 1Document itch, soreness, odour, discharge, pH where available, pelvic symptoms, pregnancy possibility and recent self-treatment.
  2. 2Examine when symptoms are atypical, severe or persistent, and obtain microscopy or targeted testing rather than relying on discharge colour alone.
  3. 3Treat a supported uncomplicated syndrome with a suitable topical or oral regimen and give explicit return advice for non-resolution.
02RecurrenceProve candidiasis before suppressionThere are at least four reported episodes yearly or rapid return after apparently adequate treatment.+
  1. 1Obtain microscopy and fungal culture during symptoms before another antifungal dose where feasible, requesting species identification and susceptibility advice if refractory.

Complications

01

Chronic vulval symptoms

Repeated inflammation and topical exposure can sustain soreness, fissuring, avoidance of sex and diagnostic uncertainty even after organisms clear.

02

Pregnancy associations

Symptomatic BV is associated with adverse pregnancy outcomes, while medicine selection for candidiasis must avoid unnecessary fetal drug exposure.

03

Antimicrobial harm

Empirical repeated treatment promotes adverse effects, ecological disturbance and delayed recognition of non-albicans yeast or a non-infective disorder.

04

Psychosexual impact

Recurrent odour, itch and pain can impair confidence, intimacy and wellbeing, requiring respectful explanation rather than hygiene-related blame.

Monitoring and follow-up

  • Expect symptom improvement after the selected course; arrange review when pain, itch, odour or discharge persists rather than issuing repeated remote prescriptions.
  • For recurrent candidiasis, record culture species, induction completion, adverse effects and response during six-month suppression, then reassess after withdrawal.
  • Check pregnancy status and medicine exposure whenever conception is possible, especially before oral fluconazole or prolonged antifungal treatment.
  • Monitor for a changing phenotype such as pelvic pain, fever, bleeding, ulceration or visible dermatosis that requires a different pathway.
  • Revisit STI testing and safeguarding according to evolving exposure history while maintaining that neither candidiasis nor BV alone proves partner infidelity.

Special situations

Colonisation is not candidiasis

Candida can be cultured from people without symptoms, so treatment requires a compatible inflammatory syndrome rather than organism detection alone.

Vaginal pH is directional

An acidic pH fits candidiasis, while a raised pH favours BV or trichomoniasis; blood, semen and sampling factors can reduce specificity.

BV has little inflammation

Prominent vulval itch, oedema or fissuring should not be casually attributed to BV and often signals Candida, trichomonas or skin disease.

Recurrence needs structure

A planned induction and maintenance course for confirmed recurrent C. albicans disease is different from repeated isolated fluconazole tablets.

Partner advice differs from STI care

Routine asymptomatic-partner treatment is unnecessary for both conditions, while a separately diagnosed STI requires its own notification and treatment pathway.

Common pitfalls

  1. 01

    Treating asymptomatic Candida growth as disease or screening well people with fungal cultures that will not change care.

  2. 02

    Diagnosing bacterial vaginosis from odour alone without considering trichomoniasis, retained foreign body or formal criteria.

  3. 03

    Prescribing oral fluconazole during pregnancy when a topical azole regimen should be selected.

  4. 04

    Calling every rapid recurrence resistant Candida without culture, species identification and reassessment of the original diagnosis.

  5. 05

    Treating asymptomatic partners routinely or implying that bacterial vaginosis is proof of a partner's outside sexual contact.

  6. 06

    Overlooking pelvic pain, contact bleeding, ulcers or visible vulval dermatosis because a vaginal swab detected a common organism.

Practice

Two practice questions

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Question 1 of 2
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Obstetrics and gynaecologyOriginal SBA

Candidiasis during pregnancy

A 29-year-old at 18 weeks' gestation has confirmed uncomplicated vulvovaginal candidiasis with troublesome itch. Which treatment approach is most appropriate?

Choose one answer, then submit
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Sources and review status3 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • BASHH vulvovaginal candidiasis guideline
  • BASHH bacterial vaginosis guideline
  • NHS vaginal discharge guidance

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

Bacterial vaginosis typically presents with a thin grey-white homogeneous discharge and fishy odour that may be more noticeable after sex or during menstruation. Amsel diagnosis requires three of four findings: characteristic discharge, pH above 4.5, clue cells and a positive amine test. Laboratory Gram-stain systems provide a reproducible alternative. Marked itch, erythema or pain should prompt a search for candidiasis, trichomoniasis, contact dermatitis or mixed disease. BV is associated with sexual activity, but it is not managed as a conventional single-pathogen STI.

For uncomplicated candidiasis, topical and oral azoles have similar effectiveness, so pregnancy, interactions, preference and local symptoms guide selection. Oral fluconazole is inappropriate in pregnancy and should be avoided when pregnancy is possible unless a reliable strategy has been considered; topical imidazole courses are used during pregnancy. Recurrent C. albicans disease is managed after confirmation with an induction regimen followed by suppressive therapy, often weekly fluconazole for six months. Non-albicans species and azole resistance require specialist microbiology because another diagnosis is often more likely than resistant yeast.

Treat symptomatic bacterial vaginosis and discuss that recurrence is common. Oral metronidazole for five to seven days is a standard option; intravaginal metronidazole gel or clindamycin cream can reduce systemic exposure but have formulation-specific counselling. Clindamycin cream can weaken latex condoms and diaphragms for several days after use. Routine male-partner treatment has not shown consistent benefit, and an asymptomatic partner does not need treatment. Offer STI testing according to sexual risk rather than assuming BV itself proves transmission from one partner.

Follow-up is symptom driven. Routine test of cure is unnecessary after clinical resolution, but persistent or early recurrent symptoms justify examination and diagnostic testing before another course. Review adherence, ongoing irritants, pregnancy, diabetes control and whether the original syndrome was correct. Explain gentle vulval care: avoid douching, perfumed products and repeated antiseptics; wash externally without vigorous cleansing. Escalate unusual bleeding, lesions, significant pelvic pain or persistent visible skin change to the appropriate cervical, vulval or pelvic pathway.

Key points

  • Candida commonly colonises the vagina without disease; treat compatible symptoms and signs, not an incidental positive culture in an asymptomatic person.
  • Vulvovaginal candidiasis usually causes pruritus, soreness, superficial dyspareunia, erythema or fissuring; discharge may be thick but is typically not offensive and pH generally remains at or below 4.5.
  • Bacterial vaginosis reflects anaerobic dysbiosis rather than tissue invasion and usually causes thin homogeneous malodorous discharge, pH above 4.5 and little vulval inflammation.
  • Diagnose bacterial vaginosis with at least three Amsel features or validated Gram-stain or molecular criteria; neither odour nor pH alone is sufficiently specific.
  • Uncomplicated candidiasis can be treated with a single intravaginal clotrimazole 500 mg pessary or oral fluconazole 150 mg once when suitable; pregnancy requires a topical azole approach rather than oral fluconazole.
  • Symptomatic bacterial vaginosis can be treated with oral metronidazole 400 mg twice daily for five to seven days; intravaginal metronidazole or clindamycin are alternatives selected for tolerability and context.
  • Routine treatment of an asymptomatic partner is not recommended for either condition; recurrent symptoms require diagnostic confirmation and review of modifiers rather than serial unsupervised single doses.
  • Recurrent candidiasis means at least four symptomatic episodes in twelve months and warrants microscopy or culture, species identification and a structured induction and maintenance plan.
  • Refractory symptoms in uncontrolled diabetes or significant immunosuppression need examination, culture and specialist-directed care.
    • Pregnancy directs candidiasis treatment toward topical azoles; a positive STI result creates separate treatment, partner-notification and follow-up obligations.
  • 05
    Glucose or immunological assessment
    Why
    Investigate a supported systemic modifier when candidiasis is severe, recurrent or unusually refractory.
    Interpretation and limitations
    Test according to symptoms and risk rather than screening every isolated episode; persistent disease still requires confirmation before attributing it to diabetes or immunosuppression.
    • 2
    AlternativeReview pregnancy, diabetes, immunosuppression, antibiotic exposure, irritants and alternative vulval diagnoses without implying that recurrence reflects poor hygiene.
  • 3For confirmed recurrent C. albicans infection, use a defined induction phase followed by six-month maintenance and reassess recurrence after stopping.
    • 03Persistent BVReassess diagnosis and recurrence driversMalodour or discharge persists or returns after an appropriate bacterial-vaginosis regimen.+
    1. 1Check adherence, reapply diagnostic criteria and test for trichomoniasis or cervical STI when exposure or inflammatory findings support them.
    2. 2Offer another recommended oral or intravaginal regimen based on tolerability, pregnancy and local guidance, explaining that recurrence is common.
    3. 3Avoid automatic partner antibiotics or repeated cleansing products, and seek specialist advice for frequent troublesome recurrence or diagnostic uncertainty.
    Key medicines and prescribing safety4 treatments · regimens, roles and cautions+
    Provides local azole treatment with minimal systemic exposure and is useful when oral fluconazole is unsuitable.

    Clotrimazole vaginal pessary

    Insert 500 mg intravaginally once for uncomplicated vulvovaginal candidiasis; use a longer topical azole course in pregnancy.

    Confirm the product instructions, avoid forceful applicator use in pregnancy, and review persistent symptoms rather than repeating doses indefinitely.

    Offers convenient systemic azole treatment when pregnancy and important interactions have been excluded.

    Fluconazole

    Take 150 mg orally as a single dose for suitable uncomplicated vulvovaginal candidiasis.

    Avoid in pregnancy; review hepatic disease, QT risk and interacting medicines, and confirm recurrent disease before prolonged off-label suppression.

    Treats anaerobic bacterial overgrowth and is a standard systemic regimen for bacterial vaginosis.

    Metronidazole

    Take 400 mg orally twice daily for five to seven days for symptomatic bacterial vaginosis.

    Discuss gastrointestinal effects, metallic taste and relevant interactions; check current product advice on alcohol and review rather than extending ineffective courses.

    Provides a local alternative for bacterial vaginosis when a vaginal treatment is preferred or oral therapy is poorly tolerated.

    Metronidazole vaginal gel

    Apply 0.75% vaginal gel once daily for five days using the supplied applicator.

    Local irritation can occur; the regimen does not treat a coexisting cervical STI and persistent symptoms need diagnostic reassessment.