What causes vaginal itching after intercourse?

Vaginal Itching After Intercourse

Vaginal itching after intercourse is most commonly caused by vulvovaginal candidiasis, bacterial vaginosis, or trichomoniasis, but you must also systematically exclude seminal plasma hypersensitivity, latex allergy, and transfer of food/drug allergens through semen. 1, 2

Diagnostic Algorithm

Step 1: Measure Vaginal pH and Perform Microscopy

• Normal pH (≤4.5) suggests vulvovaginal candidiasis or seminal plasma hypersensitivity 3, 4
• Elevated pH (>4.5) indicates bacterial vaginosis or trichomoniasis 3, 4
• Perform wet mount with saline to identify motile trichomonads or clue cells 4
• Perform KOH preparation to identify yeast pseudohyphae and conduct whiff test (fishy odor indicates bacterial vaginosis) 4

Step 2: Assess Timing and Pattern of Symptoms

• Symptoms within seconds to minutes after ejaculation strongly suggest seminal plasma hypersensitivity, which presents with diffuse pruritus, urticaria, localized vulvar/vaginal burning, itching, and swelling 1
• Symptoms that resolve with condom use confirm either seminal plasma hypersensitivity or latex allergy (if condoms fail to prevent symptoms, suspect latex allergy or incorrect condom technique) 1
• Symptoms occurring with multiple different partners suggest seminal plasma hypersensitivity rather than partner-specific allergen transfer 1

Step 3: Rule Out Allergen Transfer Through Semen

• Ask if male partner recently ingested foods (especially walnuts) or drugs (especially penicillin) to which the female partner has known allergies 1
• Inquire about exposure to other contactants like fragrant sanitary napkins 1
• Consider whether male partner recently underwent prostatectomy or vasectomy, which has been associated with reactions 1

Common Infectious Causes and Treatment

Vulvovaginal Candidiasis (Most Common with Normal pH)

• Presents with pruritus, vaginal discharge, vulvar burning, external dysuria, and painful intercourse 3, 2, 5
• Treat with oral fluconazole 150 mg single dose OR topical azoles (clotrimazole, miconazole, terconazole) for 1-7 days 1
• Note: Oil-based creams and suppositories weaken latex condoms 1

Bacterial Vaginosis

• Presents with malodorous discharge, minimal irritation, elevated pH >4.5, positive whiff test, and clue cells on microscopy 3, 4, 2
• Treat with oral metronidazole or intravaginal metronidazole/clindamycin 2, 5

Trichomoniasis

• Presents with yellow-green discharge, malodor, irritation, burning, elevated pH >4.5, and motile trichomonads on microscopy 3, 2, 5
• Diagnose with nucleic acid amplification testing (NAAT) in symptomatic or high-risk women 2
• Treat with oral metronidazole 2 grams single dose for both patient and sexual partners 5

Seminal Plasma Hypersensitivity Workup (When Infectious Causes Excluded)

High-Risk Populations

• Women with history of allergic asthma or atopic dermatitis are at highest risk 1
• Can occur postpartum, after gynecologic surgery, or after anti-Rh immune globulin injection 1
• Can occur after first coital act or with multiple previous encounters 1

Diagnostic Confirmation

• Perform skin prick testing with whole seminal plasma from male partner (most sensitive diagnostic test) 1
• Screen male donor for viral hepatitis, syphilis, and HIV before skin testing 1
• Prepare fresh seminal plasma by allowing ejaculate to liquefy at room temperature, centrifuge at 4°C, and filter sterilize 1
• Positive response defined as wheal ≥3 mm greater than saline control with flare, and negative response in male donor 1
• Serum specific IgE testing (RAST/ELISA) is less sensitive than skin testing; negative result does not exclude sensitization 1

Treatment of Confirmed Seminal Plasma Hypersensitivity

• Barrier use of condoms prevents reactions 1
• Immunotherapy to properly fractionated seminal fluid proteins is universally successful in preventing anaphylaxis 1
• Intravaginal graded challenge with unfractionated seminal fluid has been reported successful in some cases, but duration of protection is unknown 1
• Localized seminal plasma hypersensitivity does not increase risk of future systemic anaphylaxis and is not associated with infertility 1

Critical Pitfalls to Avoid

• Do not empirically treat without diagnostic testing, as this leads to more frequent return visits and delays correct diagnosis 4, 2
• Do not assume symptoms are infectious without confirming elevated vaginal pH or positive microscopy 3, 4
• Do not overlook latex allergy if condom use fails to prevent symptoms 1
• Partner treatment is not indicated for vulvovaginal candidiasis or bacterial vaginosis, but is required for trichomoniasis 1, 5
• Self-medication with over-the-counter antifungals should only occur in women previously diagnosed with vulvovaginal candidiasis who have recurrence of identical symptoms 1