Heat Rash (Miliaria) — Management

Overview

Miliaria results from obstruction of eccrine sweat ducts due to heat and humidity, causing sweat to escape into surrounding tissue. Three distinct types are recognized based on the depth of ductal obstruction.

Miliaria crystallina: delicate, droplike vesicles with no underlying erythema

Types and Clinical Features

Type	Obstruction Level	Lesions	Symptoms
Crystallina	Stratum corneum	Clear, fragile 1 mm vesicles	Asymptomatic; rupture easily
Rubra (prickly heat)	Mid-epidermis	Erythematous 1–3 mm papulovesicles; may become pustular	Pruritic, prickling/burning sensation
Profunda	Dermal–epidermal junction	Flesh-colored/white 1–3 mm papules	Asymptomatic; resolves within 1–2 hrs of stopping exertion

Management by Type

Miliaria Crystallina

No treatment required — lesions are self-limited, rupture spontaneously with minimal trauma, and carry no systemic risk. — Andrews' Diseases of the Skin, p. 34

Miliaria Rubra

The cornerstone of management is environmental control:

Move to a cool environment — even a single night in an air-conditioned room substantially relieves symptoms. This is the most effective measure.
Air circulation — fans to cool the skin surface.
Remove occlusive clothing — avoid tight or non-breathable fabrics.
Treat underlying febrile illness if present.
Soothing baths — colloidal oatmeal or cornstarch baths used in moderation.
Dusting powders — cornstarch or baby talcum powder for mild cases.
Hydrophilic ointment — helps dissolve keratinous plugs and facilitates normal sweat flow.

Miliaria Profunda

Anhydrous lanolin applied topically has produced dramatic improvement — it resolves poral occlusion and may help restore normal sweat secretion.
Relocate to a cool environment; lesions typically subside within 1–2 hours of cessation of sweating.

— Andrews' Diseases of the Skin, p. 35; Fitzpatrick's Dermatology, p. 1496

General Principles for All Types

Intervention	Rationale
Cool environment / air conditioning	Reduces sweating stimulus; allows duct occlusion to resolve
Remove occlusive dressings/clothing	Eliminates maceration of stratum corneum that causes duct blockage
Avoid excessive heat/humidity exposure	Primary prevention and treatment
Treat fever	Reduces sweating that perpetuates occlusion

Special Populations

Neonates: Place in a cooler environment or remove tight clothing/swaddling. Incubator-related cases resolve once temperature is adjusted. — Harriet Lane Handbook, p. 286
Tropical climates / repeated bouts: Miliaria rubra can progress to miliaria profunda. Individuals with extensive profunda are at risk for thermoregulatory failure (tropical anhidrotic asthenia) due to widespread anhidrosis — cooling and avoidance of exertion in heat are critical.

Postmiliarial Hypohidrosis

An important complication: sweating may be depressed to half normal for up to 3 weeks after resolution, impairing heat tolerance. Affected individuals may experience irritability, vertigo, anorexia, and headache. Avoid heat stress during the recovery period. — Andrews' Diseases of the Skin, p. 35

What to Avoid

Topical corticosteroids are not indicated for routine heat rash.
Avoid continued occlusion (tight clothing, adhesive dressings).
Excessive use of powders can paradoxically worsen occlusion if overused.

Sources: Andrews' Diseases of the Skin (9780323547536) | Fitzpatrick's Dermatology Vol. 1–2 (9780071837781) | Dermatology 2-Volume Set 5e (9780702082252) | Harriet Lane Handbook 23e (9780323876988)

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