Which sexually transmitted infection(s) can cause genital itching?

Which STDs Cause Genital Itching?

The sexually transmitted infections most commonly associated with genital itching are trichomoniasis, genital herpes (HSV), pubic lice (pediculosis pubis), and scabies, with vulvovaginal candidiasis (though not always sexually transmitted) also being a frequent cause of vulvar itching in women. 1, 2, 3

Primary STI Causes of Itching

Trichomoniasis

Trichomoniasis is strongly associated with vulvar itching in women. In a clinical study, vulvar itching had an adjusted odds ratio of 3.0 for trichomoniasis infection, even after controlling for coinfections 3. Women typically present with:

• Yellow or green frothy vaginal discharge
• Vulvar itching (significant symptom)
• Vaginal and vulvar erythema
• "Strawberry cervix" (colpitis macularis) on examination 3

The diagnosis requires wet mount microscopy showing motile trichomonads, though culture or nucleic acid amplification tests (NAAT) are more sensitive 1. Treatment is oral metronidazole or tinidazole 4.

Genital Herpes (HSV-1 or HSV-2)

Genital herpes can cause itching, particularly during primary infection or recurrent episodes 5, 6. The presentation includes:

• Vesicular and ulcerative lesions on genitals, buttocks, or thighs
• Itching or burning sensation
• Painful ulcers that crust and heal spontaneously 5

Diagnosis should be confirmed with type-specific molecular or virologic tests when lesions are present 6. Management includes episodic or suppressive antiviral therapy.

Ectoparasitic Infections

Pediculosis Pubis (Pubic Lice): Patients seek care primarily because of pruritus and notice lice on pubic hair 2. Treatment options include:

• Permethrin 1% cream rinse (applied and washed off after 10 minutes)
• Lindane 1% shampoo (4 minutes, not for pregnant/lactating women or children <2 years)
• Pyrethrins with piperonyl butoxide 2

Scabies: Presents with severe pruritus, papular or vesicular rash, and linear burrows in finger webs and genital area 7. Treatment is lindane 1% or synthetic pyrethrins 7.

Secondary Considerations

Vulvovaginal Candidiasis

While not always sexually transmitted, candidiasis frequently causes vulvar itching and is commonly diagnosed during STI evaluations 1, 8. It presents with:

• White, thick, curd-like discharge
• Intense pruritus
• Vulvar erythema 4

Diagnosis is by visualization of yeast hyphae on microscopy or culture 4.

Cervicitis-Related Itching

Mucopurulent cervicitis from Chlamydia trachomatis or Neisseria gonorrhoeae can occasionally cause vaginal discharge and associated irritation, though itching is not a primary symptom 9, 1.

Clinical Approach

When evaluating genital itching:

1. Examine for visible parasites (lice, nits) or burrows (scabies)
2. Assess for vesicular/ulcerative lesions suggesting herpes
3. Perform wet mount microscopy to identify motile trichomonads or yeast
4. Check vaginal pH: elevated pH (>4.5) suggests trichomoniasis or bacterial vaginosis 8
5. Consider NAAT testing for trichomoniasis if microscopy is negative but symptoms persist 9

Important caveat: Itching with minimal discharge and no identifiable pathogens may indicate mechanical, chemical, allergic, or other noninfectious irritation 1, 8. In these cases, avoid repeated antimicrobial courses and consider alternative etiologies.

The presence of itching should prompt specific testing rather than empiric treatment, as the sensitivity of symptoms alone is relatively low for predicting specific infections 3.