Management of Allergic Dermatitis

Allergic Contact Dermatitis (ACD)

Step 1: Identify and Remove the Allergen

• Carefully review history for occupational, cosmetic, jewelry, or topical medication exposures
• Patch testing applies standard allergen panels to the skin for 48-96 hours; readings at 48 and 96 hours (or day 7)
• In occupational ACD (nickel, chromium), avoidance may require a change of work environment

Step 2: Acute Phase Treatment

• Topical corticosteroids (creams, lotions, or ointments) twice daily - the first-line local treatment
• Moisturize with ointments (Vaseline, Aquaphor) twice daily
• Oral antihistamines and/or oatmeal baths for pruritus (sedating antihistamines at bedtime for sleep)

• Systemic corticosteroids: prednisone 40-60 mg/day orally in a single dose, then taper slowly over 2-3 weeks
• Short courses must be avoided - the eruption will flare when the drug is stopped prematurely
• For poison ivy specifically: remove clothing and wash skin with mild soap and water as soon as possible

Atopic Dermatitis (AD) - Eczema

General/Lifestyle Measures

• Trigger avoidance: alcohol-containing products, fragrances, astringents, excessive sweating, scratching
• Bathing: less than 5 minutes in lukewarm water, gentle bar soap, no scrubbing; pat dry and immediately apply emollient ("soak and smear" technique)
• Skin hydration: frequent bland emollients with minimal water content (Vaseline or Aquaphor); avoid lotions with high water content
• Dilute bleach baths once or twice weekly (1/4 cup bleach in a full tub, 10-minute soak) to reduce secondary bacterial colonization/infection

Pharmacologic Treatment (Stepwise)

Step 1 - Mild Disease: Topical Corticosteroids (TCS)

• Low- to medium-potency steroid ointments once or twice daily during flares (7-day courses)
• Severe flares may require high-potency steroids with subsequent taper to low-potency
• Do not use fluorinated corticosteroids on the face or intertriginous areas - risk of cutaneous atrophy
• For face/flexures: milder preparations such as 0.025% triamcinolone ointment
• ~80% of patients improve with topical steroid therapy

Step 2 - Moderate Disease: Topical Calcineurin Inhibitors (TCIs)

• Tacrolimus ointment (0.03% for children; 0.1% for adults) - stronger anti-inflammatory effect
• Pimecrolimus cream 1% - more skin-selective, used in milder cases
• Three-times-weekly tacrolimus reduces relapse in stabilized AD ("proactive therapy")
• Should be used in consultation with a specialist in children

Step 3 - Moderate-to-Severe: Systemic Therapies

Step 4 - Severe/Refractory: Biologics

• Dupilumab (Dupixent): IL-4/IL-13 receptor antagonist; FDA-approved (2017) as the first biologic for moderate-to-severe AD not adequately controlled by topical therapy
  • Dose: 300 mg SC every 2 weeks (after loading dose) in adults
  • Achieves ≥68% reduction in EASI score in clinical trials vs. 17% placebo
  • Pruritus improves rapidly, sometimes within 4 weeks
  • Safety profile comparable to or better than cyclosporine; slight increase in herpes virus infections noted
  • Avoid in pregnancy (no safety data)

Managing Complications

• Secondary bacterial infection (Staphylococcus aureus): bleach baths prophylactically; topical or systemic antibiotics if infected
• Eczema herpeticum (HSV superinfection): requires urgent systemic antiviral therapy (acyclovir)
• Eczema molluscum: treat underlying eczema; molluscum may resolve with AD control
• Topical corticosteroid allergy: suspect if dermatitis is not improving as expected (paradoxical flare) - patch test to corticosteroid series

Summary Algorithm

ACD
├── Identify & avoid allergen (patch test if unclear)
├── Topical steroids (mild/moderate)
└── Systemic prednisone 40-60mg/day + taper (severe/widespread)

Atopic Dermatitis
├── Emollients + trigger avoidance (all stages)
├── Mild: Low/medium TCS → TCI (face/flexures)
├── Moderate: Medium/high TCS + TCI second-line
├── Severe: Systemic (cyclosporine, MTX) + UV-B
└── Refractory: Dupilumab 300mg SC q2 weeks

Recent guideline update (2025): A focused update to the AAD Guidelines for Atopic Dermatitis in Adults (PMID 40531067, J Am Acad Dermatol, 2025) is now available and may include expanded indications for newer biologics and JAK inhibitors (abrocitinib, upadacitinib, baricitinib) that are not fully covered in the textbook sources above.

Fexofenadine in Allergic Dermatitis

• Antihistamines help with itch in dermatitis, but do not directly impact the rash itself
• The benefit is partly from their sedating effect at night, which breaks the itch-scratch cycle
• Non-sedating agents like fexofenadine are less effective for the itch of atopic dermatitis than sedating antihistamines (like hydroxyzine or chlorpheniramine), because the itch in AD is not purely histamine-mediated

Levocetirizine in Allergic Dermatitis

Calamine Lotion in Allergic Dermatitis

"Acute and subacute pruritic dermatoses, especially acute allergic contact dermatitis"

Summary Table