What is the best treatment approach for a patient with heat rash, considering potential allergies or pre-existing medical conditions such as eczema?

Heat Rash Treatment

First-Line Treatment Approach

For heat rash (miliaria), the primary treatment is cooling the skin and removing heat exposure, combined with topical hydrocortisone 1% applied 3-4 times daily to reduce inflammation and itching. 1

• Apply over-the-counter hydrocortisone 1% cream or ointment to affected areas 3-4 times daily for symptomatic relief of itching and inflammation 1
• Immediately move the patient to a cool environment and remove any occlusive clothing or heat sources 2
• Use cool compresses or tepid water baths to lower skin temperature—avoid hot water which worsens the condition 2

Essential Supportive Skin Care

• Apply fragrance-free emollients after bathing to damp skin to create a protective barrier and prevent transepidermal water loss 3, 4
• Use mild, pH-neutral (pH 5) non-soap cleansers or dispersible creams as soap substitutes to preserve the skin's natural lipid barrier 3, 4
• Pat skin dry with clean towels rather than rubbing to minimize irritation 4
• Keep the affected area dry and well-ventilated—moisture and occlusion perpetuate heat rash 2

Special Considerations for Patients with Pre-existing Eczema

• If the patient has underlying atopic eczema, apply moderate-potency topical corticosteroids (not just hydrocortisone 1%) twice daily to all eczematous areas while managing the heat rash 4
• Continue aggressive emollient therapy at least 3-4 times daily to the entire body, using thick ointments or creams rather than lotions 4
• Watch carefully for secondary bacterial infection (increased crusting, weeping, pustules) which requires oral flucloxacillin while continuing topical corticosteroids 4, 5
• Be vigilant for eczema herpeticum if grouped vesicles, punched-out erosions, or sudden deterioration with fever develop—this requires immediate intravenous acyclovir 5, 6

Managing Pruritus

• Prescribe sedating antihistamines (such as hydroxyzine or diphenhydramine) exclusively at nighttime for severe itching, as their benefit comes from sedation rather than direct anti-pruritic effects 4
• Non-sedating antihistamines have no value in heat rash or eczema and should not be used 4

Critical Warnings and Limitations

• Do not use hydrocortisone for more than 7 days without physician supervision—stop use if condition worsens or symptoms persist beyond 7 days 1
• Avoid contact with eyes and do not apply to broken or infected skin without concurrent antimicrobial therapy 1
• In children under 2 years of age, consult a physician before using topical hydrocortisone 1
• Do not use hydrocortisone for diaper rash 1

Prevention of Recurrence

• Avoid prolonged exposure to heat sources, including space heaters, heated car seats, and hot environments 2, 7
• Wear loose-fitting, breathable cotton clothing rather than synthetic or occlusive fabrics 2
• Avoid greasy or occlusive creams that can facilitate folliculitis and worsen heat retention 4
• Keep nails short to minimize trauma from scratching 4

When to Seek Further Medical Attention

• If symptoms persist beyond 7 days despite appropriate treatment 1
• If signs of secondary infection develop (increased crusting, weeping, pustules, or fever) 4, 5
• If grouped vesicles or punched-out erosions appear, suggesting possible eczema herpeticum 5
• If the patient has underlying eczema that fails to respond to moderate-potency topical corticosteroids after 4 weeks 4