What are the possible causes of vaginal itching in a patient, considering factors such as age, sexual activity, medical history, and potential underlying conditions like yeast infections, bacterial vaginosis, or hormonal changes?

Possible Causes of Vaginal Itching

The three most common infectious causes of vaginal itching are vulvovaginal candidiasis (20-25% of cases), bacterial vaginosis (40-50%), and trichomoniasis (15-20%), with non-infectious causes including chemical irritation, atrophic vaginitis, and allergic reactions accounting for 5-10% of cases. 1, 2

Infectious Causes

Vulvovaginal Candidiasis (Yeast Infection)

• Most common presentation: Intense vulvar pruritus with thick white "cottage cheese" discharge, vaginal soreness, burning, and dyspareunia 1
• Key diagnostic feature: Normal vaginal pH (≤4.5) distinguishes this from other infections 1
• Approximately 75% of women experience at least one episode during their lifetime 1
• Diagnosis confirmed by visualizing yeasts or pseudohyphae on KOH wet mount or culture 1, 2
• Important caveat: 10-20% of asymptomatic women harbor Candida species normally, so identification without symptoms should not prompt treatment 1

Bacterial Vaginosis

• Presentation: Homogeneous thin white discharge with characteristic fishy odor, though 50% of women meeting diagnostic criteria are asymptomatic 1, 2
• Diagnostic features: Elevated vaginal pH (>4.5), positive whiff test (fishy odor with KOH), and clue cells on microscopy 1, 3
• Results from replacement of normal H₂O₂-producing Lactobacillus species with anaerobic bacteria and Gardnerella vaginalis 1, 3
• Key distinction: Lacks significant vulvar inflammation compared to candidiasis or trichomoniasis 4

Trichomoniasis

• Classic presentation: Frothy greenish discharge with prominent itching and vulvar inflammation 4
• Elevated vaginal pH (>4.5) and positive whiff test, similar to bacterial vaginosis 1, 3
• Motile trichomonads visible on saline wet mount, though culture is more sensitive 2, 5
• Critical point: This is a sexually transmitted infection requiring partner treatment to prevent reinfection 1, 4

Non-Infectious Causes

Chemical and Mechanical Irritation

• Presentation: Vulvar inflammation with minimal discharge in the absence of identifiable pathogens 1
• Common irritants include soaps, douches, perfumed products, and tight synthetic clothing 3
• Regular soap can cause symptoms identical to infectious vaginitis, leading to unnecessary antimicrobial treatment 3
• Management: Discontinue irritants, avoid douching, use only water or mild soap for external cleansing 3

Atrophic Vaginitis

• Results from estrogen deficiency, typically in postmenopausal women 2
• Presents with vaginal dryness, burning, and dyspareunia 2
• Requires hormonal or non-hormonal therapies directed at underlying cause 2

Cervicitis

• Mucopurulent cervicitis from Chlamydia trachomatis or Neisseria gonorrhoeae may uncommonly cause vaginal discharge and irritation 1

Diagnostic Approach

Essential initial tests include:

• Vaginal pH measurement (normal 3.8-4.2; elevated >4.5 suggests bacterial vaginosis or trichomoniasis) 3
• Saline wet mount to identify motile trichomonads or clue cells 1
• KOH preparation to visualize yeast/pseudohyphae and perform whiff test 1
• Visual inspection for foreign bodies, atrophic changes, or chemical irritation 3

Critical pitfall: Symptoms alone cannot reliably distinguish between causes—microscopic examination is essential, as presenting symptoms and signs have limited diagnostic value 2, 6

Special Considerations

Immunocompromised Patients

• Patients with conditions causing immunosuppression (e.g., Cushing's syndrome, HIV/AIDS) experience more severe and recurrent candidiasis 7
• These patients require classification as complicated vulvovaginal candidiasis with extended therapy (7-14 days topical azoles or fluconazole 150mg repeated after 3 days) 7
• Do not use short-course 1-3 day therapy in immunocompromised patients 7

Mixed Infections

• It is not uncommon for women to have more than one microbial cause simultaneously 5
• Vulvovaginal candidiasis may be present concurrently with STDs 1

Diagnostic Limitations

• Laboratory testing fails to identify a cause in approximately 50% of symptomatic women 1, 6