Diagnosis and Treatment of Underarm Rash in 38-Year-Old Female
Diagnosis
This presentation is most consistent with inverse (intertriginous) candidiasis, not dermatophyte infection, given the location (both armpits), failure to respond to topical azoles and terbinafine, and evolution to whitish dry scales on bumpy red papules worsened by moisture. 1
Key Diagnostic Features Supporting Candidiasis:
- Bilateral axillary involvement with scaly dry lesions on erythematous papular base is classic for intertriginous candidiasis 1
- Worsening with sweat indicates moisture-dependent pathogen, characteristic of Candida species 1
- Failure to respond to terbinafine and clotrimazole after one week suggests non-dermatophyte etiology, as dermatophytes typically show some response to these agents 2, 3
- Whitish dry scales can represent secondary changes from scratching and chronic inflammation in candidal infections 1
Critical Pitfall to Avoid:
The initial circular red lesion may have mimicked tinea corporis, but the axillary location, bilateral presentation, and moisture-exacerbation strongly favor Candida over dermatophytes. Calamine lotion should never have been used, as it provides no antifungal benefit and may worsen the condition through irritation 4.
Immediate Management
Confirm Diagnosis:
- Obtain KOH preparation and fungal culture immediately to differentiate Candida from dermatophyte or mixed infection 5, 6
- Look for satellite lesions at the periphery, which are pathognomonic for candidiasis 1
First-Line Treatment for Intertriginous Candidiasis:
Topical imidazole lotions are the first-line treatment for Candida-associated skin infections 5:
- Apply topical clotrimazole 1% cream or miconazole 2% cream twice daily to affected areas for 2-4 weeks 5, 7
- Keep the area dry - this is critical as moisture disrupts the protective skin barrier and promotes Candida growth 6
- Use absorbent powder (not cornstarch-based) between applications to reduce moisture 6
If No Response After 2 Weeks:
Escalate to systemic therapy with oral itraconazole 200 mg daily for 2-4 weeks 4, 5:
- Itraconazole has broader antimicrobial coverage for Candida compared to terbinafine 4
- Terbinafine should be avoided as it has limited and unpredictable activity against Candida species 5
- Alternative: Fluconazole 100-200 mg daily if itraconazole is contraindicated, though less effective 4
Adjunctive Measures
Reduce Inflammation:
- Apply mid-potency topical corticosteroid (e.g., triamcinolone 0.1% cream) twice daily for 3-5 days only to reduce itching and inflammation 5, 6
- Discontinue after 5 days to avoid creating "tinea incognito" or promoting fungal proliferation 7, 8
Antiseptic Soaks:
- Dilute vinegar soaks (50:50 dilution) for 10-15 minutes twice daily to reduce bacterial superinfection and create acidic environment unfavorable to Candida 6
Prevention of Recurrence
Address moisture and friction 6:
- Wear loose-fitting, breathable cotton clothing
- Apply antiperspirant to reduce sweating (avoid deodorants with irritants)
- Dry armpits thoroughly after bathing
- Apply barrier cream or zinc oxide paste if friction is present
- Consider prophylactic antifungal powder during humid weather
Common Pitfalls
- Do not continue terbinafine - it is ineffective against Candida and will delay appropriate treatment 5
- Avoid prolonged topical steroid use without concurrent antifungal therapy, as this can worsen fungal infections 7, 8
- Do not assume treatment failure means resistant dermatophyte - consider alternative diagnosis (Candida, bacterial superinfection, or contact dermatitis from multiple topical agents) 8
- Reassess if no improvement after 2 weeks of appropriate antifungal therapy - obtain cultures and consider systemic therapy 6, 8