Prickly Heat

Introduction

Miliaria, also known as heat rash, sweat rash or prickly heat, is a common skin disease caused by blockage and/or inflammation of eccrine sweat ducts.

  • The blockage leads to backflow of eccrine sweat into the dermis or epidermis, resulting in a rash comprised of sweat-filled vesicles under the skin.

The type of miliaria that develops depends on the depth at which the duct is blocked.

  • Miliria crystallina - Occurs when the duct is blocked superficially, within or close to the stratum corneum.
  • Miliaria rubra - The most common type; occurs when the duct is blocked deeper within the epidermis.
  • Miliaria profunda - Occurs when the eccrine duct is blocked at or below the epidermal-dermal junction.

Prickly Heat

Common triggers include hot and humid environments (especially shortly after moving to a tropical climate), strenuous physical activity, febrile illness and occlusion of the skin.



Management

The rash is usually self-limited and resolves without medical intervention.

The primary treatment for miliaria involves cooling and drying the affected areas and avoiding conditions that induce sweating.

  • Avoid excessive heat when feasible (e.g. by limiting strenuous physical activity)
  • Wear breathable clothing (such as cotton) that does not occlude the skin, and avoid excessive layers.
  • Use air conditioning in hot and humid weather.
  • Take frequent cool showers or baths using a mild soap

Once the rash develops, calamine lotion or a mild topical corticosteroid can be applied. Preparations containing menthol can also provide a soothing, cooling effect.

  • Mild to mid-potency topical corticosteroids may be used to decrease pruritus (itching) and hasten the resolution of inflammation.
  • Topical antiseptics or anti-staphylococcal antibiotics (e.g., clindamycin or erythromycin) may be indicated if a secondary bacterial infection occurs.



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