What is the treatment for an adult with contact dermatitis resembling acne eruptions caused by exposure to methylisothiazolinone (MI) in personal care products?

Treatment of Contact Dermatitis from Methylisothiazolinone

Immediately discontinue all personal care products containing methylisothiazolinone (MI) and apply mid-to-high potency topical corticosteroids to affected areas, combined with aggressive emollient therapy to restore the skin barrier. 1

Immediate Management Steps

Complete allergen avoidance is the cornerstone of treatment and determines success or failure. 1, 2 The dermatitis will not resolve without eliminating MI exposure, regardless of how aggressive the topical therapy. 2

Identify and Eliminate MI Sources

• Check all personal care products for MI, methylchloroisothiazolinone/methylisothiazolinone (MCI/MI), and related isothiazolinones including wet wipes, facial creams, shampoos, body washes, and cosmetics. 3, 4, 5
• MI is increasingly used alone (without MCI) in leave-on and rinse-off products, making it harder to identify on labels. 4, 5
• Replace all identified products with MI-free alternatives immediately. 1
• Wet wipes are a particularly common and overlooked source of MI exposure, especially in perianal, buttock, facial, and hand dermatitis. 4

Replace Irritants with Emollients

• Substitute all soaps and detergents with emollients immediately, even if they don't contain MI, as these universal irritants perpetuate inflammation and prevent healing. 1
• Use moisturizers packaged in tubes rather than jars to prevent contamination. 1
• Apply moisturizers liberally and frequently to restore skin barrier function. 1

Topical Corticosteroid Therapy

For Body/Trunk Areas

• Apply mid-to-high potency topical corticosteroids (such as betamethasone valerate 0.1% or triamcinolone 0.1%) to affected areas 1-2 times daily. 1
• If initial treatment fails after 7-10 days, escalate to very high potency corticosteroids (clobetasol propionate 0.05%) for up to 2 weeks. 1
• Very high potency steroids achieve clear or almost clear skin in 67.2% of patients with severe dermatitis over 2 weeks. 1

For Facial Dermatitis

• Use only low-potency corticosteroids (hydrocortisone 1%) on the face due to increased percutaneous absorption and risk of steroid-induced skin damage, telangiectasia, and perioral dermatitis. 1, 6, 7
• Apply to affected facial areas not more than 3-4 times daily. 7
• Exercise extreme caution with prolonged facial steroid use—the face is particularly vulnerable to steroid-induced atrophy. 1

Diagnostic Confirmation

Patch Testing

• Refer for patch testing with an extended baseline series to confirm MI allergy and identify any co-sensitizations. 8, 1
• MI alone (without MCI) requires testing with aqueous MI 2000 ppm, which may not be included in standard trays. 9
• Some patients test positive to MI but negative to MCI/MI, so both should be tested. 9
• Defer patch testing for 6 weeks after UV exposure, 3 months after systemic immunosuppressants, and 6 months after biologics to avoid false negatives. 2
• Do not apply potent topical steroids to the back within 2 days of patch testing. 1

Second-Line Therapies for Refractory Cases

If dermatitis persists despite complete MI avoidance and topical corticosteroids:

• Consider topical tacrolimus 0.1% where topical steroids are unsuitable, ineffective, or when chronic facial dermatitis raises concerns about steroid-induced damage. 1
• PUVA phototherapy is an established second-line treatment for chronic contact dermatitis resistant to topical steroids. 1
• For severe chronic hand eczema specifically, alitretinoin is recommended. 1
• Consider systemic immunosuppressants (azathioprine, ciclosporin, methotrexate, or mycophenolate mofetil) for steroid-resistant cases. 1

Clinical Presentation Patterns

MI contact dermatitis frequently mimics other conditions:

• Facial and neck dermatitis may resemble photodermatosis with spreading eczematous eruptions. 3
• Perianal and buttock dermatitis is commonly misdiagnosed as eczema, impetigo, or psoriasis, especially in children using wet wipes. 4
• The acne-like appearance mentioned in your question likely represents papulovesicular eczematous eruptions rather than true acne, which is characteristic of acute allergic contact dermatitis. 3, 4

Cross-Reactivity and Related Allergens

• Avoid all isothiazolinones including octylisothiazolinone (OIT) and benzisothiazoline (BIT), as cross-reactivity occurs. 4, 5
• OIT and MI show cross-reactivity, and patients allergic to MI may be co-sensitized to BIT. 5
• Check for MI in non-cosmetic sources including household products, industrial chemicals, paints, adhesives, and slime products. 5

Critical Pitfalls to Avoid

• Do not continue topical antibiotics—these are frequently prescribed for misdiagnosed MI dermatitis and may themselves cause sensitization. 1, 4
• Do not rely on barrier creams alone—they have questionable value and create false security. 1
• Do not assume wet wipes are safe—they are extensively tested but increasingly contain MI and are a major source of pediatric and adult sensitization. 4
• Failure to identify and eliminate MI exposure will result in treatment-resistant dermatitis regardless of corticosteroid potency. 2

Expected Timeline and Prognosis

• Rapid and complete resolution occurs within days to weeks after eliminating MI exposure, provided all sources are identified. 4
• If dermatitis persists beyond 2-3 weeks despite confirmed MI avoidance, re-evaluate for additional allergens or consider patch testing to corticosteroids themselves. 1
• Provide written information about MI and its alternative names—only 17% of patients remember the allergen name after 10 years. 2