What is the appropriate evaluation and management for a pruritic rash on the chest?

Evaluation and Management of Pruritic Chest Rash

For a pruritic rash on the chest, apply a potent topical corticosteroid such as betamethasone valerate 0.1% or mometasone furoate 0.1% once daily, combined with regular emollient use and avoidance of hot water and skin irritants. 1

Initial Assessment

Obtain a complete medication history, including all prescription drugs, over-the-counter medications, and herbal remedies, as drug-induced pruritus occurs in 12.5% of cutaneous drug reactions and can present with or without visible rash. 2 Specifically inquire about:

• Cancer therapies: EGFR inhibitors cause acneiform rash in 75-90% of patients, typically on face, chest, and upper back within days to weeks of starting therapy 2, 3
• MEK inhibitors: Cause papulopustular eruption in 74-85% of patients 2, 3
• Opioids: Affect 2-10% of patients on oral formulations 2
• Recent transfusions or new medications 2

Examine for specific morphology:

• Follicular papules and pustules suggest drug-induced acneiform eruption, particularly in sebaceous-rich areas like the chest 2
• Erythema with scaling and visible borders indicates contact dermatitis 4
• Vesicles, bullae, or erosions require immediate evaluation for severe cutaneous adverse reactions 2
• Signs of infection: crusting, weeping, yellow discharge, or grouped punched-out erosions 1, 5

Treatment Algorithm

For Non-Drug-Induced Rash (Contact Dermatitis or Eczema)

Apply potent topical corticosteroid (betamethasone valerate 0.1% or mometasone furoate 0.1%) once daily for one month to the chest. 1 The chest has thicker skin that tolerates higher potency steroids compared to flexural areas. 1

• Apply after bathing when skin is slightly damp for better absorption 1
• After the initial month, reduce to alternate-day application for one month, then twice weekly to prevent relapse 1
• Use 15-30g of cream/ointment for a two-week period for chest and flexural areas 1

Apply emollients liberally throughout treatment as soap substitutes and moisturizers. 1 Use alcohol-free moisturizers containing 5-10% urea twice daily. 1, 5 Apply emollients at least 30 minutes before or after topical corticosteroids. 1

Implement skin care measures:

• Avoid frequent washing with hot water 1, 5
• Avoid temperature extremes 1
• Keep nails short to minimize scratching damage 1
• Wear cotton clothing next to skin; avoid wool 1
• Use dispersible cream as soap substitute instead of regular soaps 1
• Avoid skin irritants including over-the-counter anti-acne medications, solvents, and disinfectants 5

For Drug-Induced Acneiform Rash (Grade 1-2)

Continue the causative medication at current dose while initiating treatment. 2

Start oral tetracycline antibiotic for at least 6 weeks: doxycycline 100 mg twice daily OR minocycline 50 mg twice daily OR oxytetracycline 500 mg twice daily. 2 These provide both antimicrobial and anti-inflammatory effects. 5

Apply topical low-to-moderate potency corticosteroid (hydrocortisone 2.5% or alclometasone 0.05%) twice daily to affected areas. 2, 5 Do not use high-potency steroids initially for drug-induced rash.

Use alcohol-free moisturizers containing 5-10% urea twice daily to maintain skin barrier function. 5

Apply sunscreen SPF 15 to exposed areas and reapply every 2 hours when outside. 2

Reassess after 2 weeks; if reactions worsen or do not improve, escalate to medium-high potency topical corticosteroids. 2, 5

For Severe or Grade 3 Rash

Hold the causative medication until rash improves to grade 1. 2

Initiate oral prednisone 0.5-1 mg/kg body weight for 7 days with tapering over 4-6 weeks. 2 For immune checkpoint inhibitor-related rash covering >30% body surface area with moderate-to-severe symptoms, use prednisone 1 mg/kg/day. 2

Continue oral antibiotics and topical corticosteroids as above. 2

Consider phototherapy for severe pruritus without adequate response to other treatments. 2

For pruritus without rash (Grade 3), consider gabapentin, pregabalin, aprepitant, or dupilumab. 2

Management of Bacterial Superinfection

Bacterial colonization or superinfection develops in up to 38% of drug-induced acneiform eruptions. 2, 3 Suspect infection when there is:

• Failure to respond to oral antibiotics covering gram-positive organisms 2
• Painful skin lesions 2
• Pustules on arms, legs, and trunk 2
• Yellow crusts or discharge 2, 1

Obtain bacterial culture before starting antibiotics. 2, 5 Administer antibiotics for at least 14 days based on sensitivity results; flucloxacillin is usually most appropriate for Staphylococcus aureus. 2, 1

When to Refer

Refer to dermatology if:

• No improvement after 4 weeks of appropriate treatment 1
• Autoimmune skin disease is suspected 2
• Rash fails to respond to first-line topical treatment and oral antibiotics within 6 weeks 5
• Skin biopsy is needed for diagnosis 2

Consider dermatology consultation for skin biopsy if the diagnosis remains unclear or if severe cutaneous adverse reactions are suspected. 2

Critical Pitfalls to Avoid

Do not use very potent steroids on flexural areas due to high risk of skin atrophy, but potent steroids are appropriate for the chest. 1

Do not discontinue emollients even when the rash is controlled, as they have a steroid-sparing effect. 1

Do not use oral antihistamines as primary treatment for atopic dermatitis-related pruritus, as evidence shows they do not reduce pruritus. 6 However, they may be useful adjuncts for drug-induced pruritus. 2

Do not rapidly discontinue systemic steroids in severe cases, as this can cause rebound dermatitis; taper over at least 4 weeks. 2, 4

Do not overlook medication history, as drug-induced pruritus is common and may occur with or without visible rash. 2