Diagnosis: Irritant Contact Dermatitis
This is irritant contact dermatitis caused by the new bathing soap, and you should immediately discontinue the soap, switch to a mild pH-neutral non-soap cleanser, apply hydrocortisone 1% cream 3-4 times daily to the affected areas, and use fragrance-free moisturizers after bathing. 1, 2
Understanding the Diagnosis
The bilateral axillary distribution with clear temporal relationship to changing bathing soap strongly indicates irritant contact dermatitis rather than allergic contact dermatitis. 1, 3 The axillae are particularly vulnerable because:
- Soaps and detergents remove natural lipids from the skin surface, causing irritation 1, 4
- The area experiences friction and occlusion, which amplifies irritant effects 1
- Irritant contact dermatitis is more common than allergic contact dermatitis and typically presents with this pattern 1, 5
The asymmetry (worse on left) is common in irritant dermatitis and doesn't require special concern—it likely reflects differences in soap application, friction, or baseline skin condition. 1, 5
Immediate Treatment Steps
Stop the Offending Agent
- Discontinue the new soap immediately and completely 3, 6
- Avoid all harsh soaps, detergents, and fragranced products in the affected areas 1, 7
Topical Corticosteroid Therapy
- Apply hydrocortisone 1% cream to affected areas 3-4 times daily for 1-2 weeks 2, 3
- This is FDA-approved for rashes due to soaps and detergents 2
- For localized acute contact dermatitis, mid-potency topical steroids like hydrocortisone are first-line 3
- Avoid using for more than 2-4 weeks continuously to prevent skin atrophy 7
Gentle Cleansing Protocol
- Use mild, pH-neutral (pH 5) non-soap cleansers or dispersible creams as soap substitutes 7, 4
- Bathe in warm (not hot) water 4
- Pat skin dry gently rather than rubbing 7
Moisturization Strategy
- Apply fragrance-free emollients containing petrolatum or mineral oil immediately after bathing to damp skin 7, 4
- This creates a surface lipid film that prevents transepidermal water loss 4
- Reapply moisturizer every 3-4 hours 7
What to Avoid
Critical pitfalls that will worsen the condition:
- Do not use alcohol-containing preparations on the affected areas—these significantly worsen dryness 7
- Avoid deodorants and antiperspirants in the affected axillae until healed 7
- Do not use hot water for bathing 7, 4
- Avoid greasy or occlusive products that can promote folliculitis 7
Expected Timeline and Follow-Up
- Improvement should occur within 3-7 days of stopping the soap and starting treatment 3, 6
- If no improvement after 4 weeks of appropriate treatment, consider patch testing to rule out allergic contact dermatitis 1, 3
- Watch for signs of secondary bacterial infection (increased crusting, weeping, pustules) which would require oral antibiotics like flucloxacillin 7
When to Escalate Care
Refer to dermatology if: 7
- No response after 4 weeks of appropriate first-line therapy
- Diagnostic uncertainty remains
- Symptoms worsen despite treatment
- Signs of secondary infection develop
The key distinction here is that irritant contact dermatitis resolves with avoidance and supportive care, whereas allergic contact dermatitis requires identification of the specific allergen through patch testing. 1, 3 Since this presentation is classic for irritant dermatitis with clear temporal relationship to soap change, patch testing is not immediately necessary unless the condition fails to resolve. 3, 5