What treatment and testing are recommended for a patient with painful, open genital blisters suspected to be caused by an allergic reaction or genital herpes, exacerbated by nappy rash cream and scented nappy wipes?

Management of Painful Genital Blisters via Telehealth

Immediately discontinue the nappy rash cream and scented wipes, as these are likely exacerbating an irritant contact dermatitis, and arrange urgent in-person evaluation or home testing kit for HSV PCR swab collection from active lesions, as laboratory confirmation is essential and clinical diagnosis alone is unreliable. 1, 2

Immediate Actions

Stop Irritant Exposure

• Instruct the patient to immediately cease using nappy rash cream and scented nappy wipes, as these products contain fragrances and occlusive ingredients that can cause or worsen irritant contact dermatitis in the genital area. 3
• Advise gentle cleansing with plain water only and patting the area dry rather than rubbing. 3

Arrange Diagnostic Testing

• Order HSV PCR (nucleic acid amplification testing) with HSV typing from vesicular or ulcerative lesions as the preferred diagnostic test, offering >90% sensitivity and specificity with results in approximately 2 hours. 2, 4
• Testing must occur as early as possible in the disease course, as vesicular lesions yield significantly higher positivity rates than ulcerative or healing lesions. 2
• If in-person evaluation is not immediately feasible, arrange a home testing kit or urgent clinic visit within 24 hours, as specimen collection requires proper technique. 2, 4

Specimen Collection Instructions (If Home Kit or Urgent Visit)

For vesicular (blister) lesions:

• Open vesicles with a sterile needle, collect vesicular fluid with a cotton-wool or Dacron swab, then vigorously swab the base of the lesion to obtain epithelial cells, which increases detection rates to 90% with viral culture and even higher with PCR. 1, 4

For ulcerative (open) lesions:

• Vigorously swab the base of ulcers using a cotton-wool or Dacron swab to collect epithelial cells and introduce into transport media for PCR testing. 1

Pain Management

Prescribe oral analgesics immediately for symptom relief:

• Start with acetaminophen 500-1000 mg every 6 hours or ibuprofen 400-600 mg every 6-8 hours for pain control. 5
• Consider adding topical lidocaine 2% gel applied to lesions 3-4 times daily for localized pain relief (avoid benzocaine due to sensitization risk). 5

Empiric Antiviral Therapy

Initiate empiric oral acyclovir 400 mg three times daily (or 200 mg five times daily) for presumed primary genital herpes while awaiting test results, as early treatment within 72 hours of symptom onset significantly reduces duration of acute infection, lesion healing time, pain duration, and new lesion formation. 6, 5, 7

Alternative dosing options:

• Valacyclovir 1000 mg twice daily (preferred for better bioavailability and compliance)
• Famciclovir 250 mg three times daily 5, 7

Treatment duration: Continue for 7-10 days for primary outbreak. 6, 5

Differential Diagnosis Considerations

While HSV is most likely, other causes of genital ulceration must be excluded:

• Syphilis (Treponema pallidum) - order RPR/VDRL and treponemal-specific testing 1, 4
• Chancroid (Haemophilus ducreyi) - less common but possible 1, 4
• Non-infectious causes including Behçet syndrome, Crohn disease, or fixed drug eruption should be considered if HSV testing is negative 1

Follow-Up Testing Strategy

If initial HSV PCR is negative but clinical suspicion remains high:

• Obtain type-specific HSV serology (glycoprotein G-based) at 12-16 weeks after symptom onset, as acute serology may be negative in primary infection. 4
• Note that HSV-1 EIA/CLIA assays have only 70.2% sensitivity (frequent false-negatives), and HSV-2 assays with index values 1.1-2.9 have only 39.8% specificity. 2

Critical Counseling Points

If HSV is confirmed, provide type-specific counseling:

• HSV-2 has 90% 12-month recurrence rate versus HSV-1 with 55% recurrence rate, making typing essential for prognosis. 2
• Asymptomatic viral shedding occurs and can transmit infection even without visible lesions. 5, 8
• Suppressive antiviral therapy (acyclovir 400 mg twice daily) reduces recurrence frequency by >95% and reduces transmission to uninfected partners. 6, 5

Common Pitfalls to Avoid

• Never rely on clinical diagnosis alone - laboratory confirmation prevents both false positive and false negative diagnoses. 1, 2
• Do not delay antiviral therapy waiting for test results - treatment is most effective when started within 48-72 hours of rash onset. 6, 5
• Do not use topical corticosteroids on suspected HSV lesions - these can worsen viral infection and delay healing. 3
• Be aware that acyclovir hypersensitivity reactions can occur (though rare), manifesting as skin rashes; graded challenge protocols exist if this develops. 9

Arrange In-Person Evaluation If:

• Severe pain uncontrolled with oral analgesics
• Signs of urinary retention or inability to void
• Systemic symptoms (high fever, severe malaise, headache suggesting meningitis)
• Immunocompromised status
• Pregnancy 5, 7