What could be the cause of redness and itching of the vulva in a female patient?

Causes of Vulvar Redness and Itching

The three most common infectious causes of vulvar redness and itching are vulvovaginal candidiasis (VVC), bacterial vaginosis (BV), and trichomoniasis, with VVC being the most likely when itching is the predominant symptom. 1

Primary Infectious Causes

Vulvovaginal Candidiasis (Most Likely with Itching)

• Vaginal itching is the most specific symptom of VVC and may be the only complaint in some cases. 1
• Additional symptoms include vaginal soreness, swelling, painful intercourse, burning with urination, or thick white discharge resembling cottage cheese. 2
• Vulvar or vaginal erythema is commonly present. 3
• VVC accounts for 20-25% of vaginitis cases when a cause is identified. 4
• Vaginal pH is typically ≤4.5, which helps distinguish it from other infections. 1

Bacterial Vaginosis

• BV is characterized primarily by malodorous discharge with minimal irritation, making it less likely when redness and itching are prominent. 1
• Vaginal pH is >4.5, and clue cells are present on microscopy. 1
• BV is the most prevalent cause of vaginal discharge overall (40-50% of cases), but up to 50% of women with BV are asymptomatic. 5

Trichomoniasis

• Presents with profuse yellow-green discharge, dysuria, and vulvar irritation. 1
• Vaginal pH is >4.5, and motile trichomonads may be visible on wet mount. 6
• Accounts for 15-20% of vaginitis cases. 4

Noninfectious Causes

Contact Dermatitis/Irritant Vaginitis

• The presence of external vulvar inflammation with minimal discharge in the absence of vaginal pathogens suggests mechanical, chemical, or allergic irritation. 1, 7
• This is an important consideration when laboratory testing fails to identify an infectious cause. 8

Vulvar Eczema

• A common chronic dermatosis causing vulvar pruritus that requires restoration of epidermal barrier function and suppression of inflammation. 1

Diagnostic Approach

Essential First Steps

• Laboratory confirmation is recommended before treatment, especially for first episodes. 1
• Symptoms alone cannot reliably distinguish between causes of vaginitis. 1, 9
• Vaginal pH testing is critical: pH ≤4.5 suggests VVC, while pH >4.5 suggests BV or trichomoniasis. 1

Microscopic Examination

• Perform wet mount microscopy with normal saline to identify motile trichomonads or clue cells. 8
• Use 10% KOH preparation to identify yeast or pseudohyphae (more easily visualized than in saline). 8
• Perform whiff test: a fishy amine odor after applying KOH suggests BV or trichomoniasis. 8

Important Caveats

• Approximately 10-20% of women normally harbor Candida species without symptoms, so treatment should be based on both symptoms and laboratory findings. 1
• Mixed infections are common and may require combination therapy. 1
• Laboratory testing fails to identify a cause in 10-50% of symptomatic women. 4, 9
• Culture for Candida or Trichomonas is more sensitive than microscopy but should be reserved for cases where microscopy is negative but clinical suspicion remains high. 8

Special Consideration for Prepubertal Children

• BV and trichomoniasis are uncommon in prepubertal children who have never been sexually active. 7
• If sexually transmitted infections are identified in a prepubertal child, sexual abuse must be considered and appropriately evaluated. 7