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Miliaria

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Miliaria, Miliaria Rubra, Miliaria Alba, Miliaria Sudamina, Apocrine Miliaria, Miliaria Crystallina, Miliaria Profunda, Heat Rash, Sweat Rash, Lichen Tropicus, Prickly Heat, Fox-Fordyce Disease

  • Epidemiology
  1. Occurs in all ages, but more common children (and 40% of newborns) whose Sweat Glands are under-developed
  • Pathophysiology
  1. Sweat retention when Eccrine Glands (Sweat Glands) partially close or are obstructed by Stratum Corneum
  2. Provoked by excessive sweating
  3. Similar pathophysiology to Milia, but these two conditions are not the same
  • Types
  • Common
  1. Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina)
    1. Typically seen in newborns (up to 90%) in first week of life
    2. Sweat infiltrates below Stratum Corneum
    3. Vessicles 1-2 mm without surrounding erythema on head, neck and trunk
      1. Noninflammatory Vesicles resemble water droplets
      2. Each vessicle ruptures and then desquamates and resolves within days
  2. Miliaria Rubra (Heat Rash, default type of Miliaria)
    1. Most common form of Miliaria, occurring in children and adults who travel to warm environments
    2. Sweat infiltrates deeper, below Epidermis
      1. Inflammation associated with Sweat Gland obstruction
    3. Pruritic erythematous Papules and Vesicles on covered (over-heated) skin
  • Types
  • Other
  1. Apocrine Miliaria (Fox-Fordyce Disease)
  2. Miliaria Profunda
    1. Asymptomatic, flesh colored, small, deep Papules on the trunk and extremities
    2. Complication of severe Miliaria Rubra occurring in hot, humid climates
  • Risk Factors
  1. Newborns (Miliaria Crystallina)
    1. Immature Sweat Glands
  2. Excessive sweating
    1. Acutely, on travel to hot, humid environments
    2. Intense Exercise
    3. Fever
    4. Occlusive clothing
    5. Hyperhidrosis
  • Symptoms
  1. Very pruritic rash
  • Signs
  • Newborns with Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina)
  1. Tiny (1-2 mm) superficial fragile Vesicles without inflammation
  2. Distributed over the head, neck and upper trunk
  • Signs
  • Children and Adults with Miliaria Rubra
  1. Characteristics
    1. Initial: Intensely pruritic, small (2-4 mm) Vesicles and Papules on erythematous base
    2. Next week: Vesicles fill keratin and obstruct Sweat Glands
    3. Next: Obstructed Sweat Glands rupture and form deeper inflammation, and may persist for weeks
  2. Distribution
    1. Children: Neck, Axilla and groin
      1. Intertriginous areas and occluded areas
    2. Adults: Scalp, neck, upper trunk and extremity flexor surfaces
      1. Areas of friction (where clothes rubs against skin)
  • Differential Diagnosis
  • Newborns with Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina)
  • Management
  1. No treatment is typically needed (esp. in newborns with Miliaria Crystallina)
    1. In newborns, resolves spontaneously in first few months of life
    2. Treat secondary infections (e.g. Impetigo)
  2. Stay in cooler environment with reduced sweating
  3. Change clothing to breathable, loosely fitting, clean, dry, cotton
  4. Avoid lotions (occlusive and may obstruct Sweat Glands)
  5. Avoid skin irritants and use only products free of perfume and dye
  • Prevention
  1. Avoid Occlusion and excessive heat
  2. Avoid over-dressing
  3. Consider cool baths (avoid prolonged exposure due to Hypothermia)
  4. Stay in cool air conditioned environments
  • Complications
  1. Chronic dermatitis
    1. May follow more severe Heat Rash
  2. Secondary Bacterial Skin Infection
    1. Superinfection, typically from scratching
  • References
  1. Salinas and Ruttan (2017) Crit Dec Emerg Med 31(9): 3-10
  2. Zink (2020) Crit Dec Emerg Med 34(3): 19-27
  3. Feng (1995) Cutis 55:213-6 [PubMed]
  4. O'Connor (2008) Am Fam Physician 77:47-52 [PubMed]