II. Epidemiology
- Occurs in all ages, but more common children (and 40% of newborns) whose Sweat Glands are under-developed
III. Pathophysiology
- Sweat retention when Eccrine Glands (Sweat Glands) partially close or are obstructed by Stratum Corneum
- Provoked by excessive sweating
- Similar pathophysiology to Milia, but these two conditions are not the same
IV. Types: Common
- Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina): Yellow Lesions
- Typically seen in newborns (up to 90%) in first week of life
- Sweat infiltrates below Stratum Corneum
- Vessicles 1-2 mm without surrounding erythema on head, neck and trunk
- Noninflammatory Vesicles resemble water droplets
- Each vessicle ruptures and then desquamates and resolves within days
- Miliaria Rubra (Heat Rash or Prickly Heat, default type of Miliaria): Red Lesions
- Most common form of Miliaria, occurring in children and adults who travel to warm environments
- Sweat infiltrates deeper, below Epidermis
- Inflammation associated with Sweat Gland obstruction
- Pruritic erythematous Papules and Vesicles on covered (over-heated) skin
V. Types: Other
- Apocrine Miliaria (Fox-Fordyce Disease)
- Miliaria Profunda
- Asymptomatic, flesh colored, small, deep Papules on the trunk and extremities
- Complication of severe Miliaria Rubra occurring in hot, humid climates
VI. Risk Factors
- Newborns (Miliaria Crystallina)
- Immature Sweat Glands
- Excessive sweating
- Acutely, on travel to hot, humid environments
- Intense Exercise
- Fever
- Occlusive clothing
- Hyperhidrosis
VII. Symptoms
- Very pruritic rash
VIII. Signs: Newborns with Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina)
- Tiny (1-2 mm) superficial fragile Vesicles without inflammation
- Distributed over the head, neck and upper trunk
IX. Signs: Children and Adults with Miliaria Rubra
- Characteristics
- Initial: Intensely pruritic, small (2-4 mm) Vesicles and Papules on erythematous base
- Next week: Vesicles fill keratin and obstruct Sweat Glands
- Next: Obstructed Sweat Glands rupture and form deeper inflammation, and may persist for weeks
- Distribution
- Children: Neck, Axilla and groin
- Intertriginous areas and occluded areas
- Adults: Scalp, neck, upper trunk and extremity flexor surfaces
- Areas of friction (where clothes rubs against skin)
- Children: Neck, Axilla and groin
X. Differential Diagnosis: Newborns with Miliaria Crystallina (Miliaria Alba, Miliaria Sudamina)
XI. Differential Diagnosis: Children and Adults with Miliaria Rubra
XII. Management
- No treatment is typically needed (esp. in newborns with Miliaria Crystallina)
- In newborns, resolves spontaneously in first few months of life
- Individual lesions resolve in days
- Treat secondary infections (e.g. Impetigo)
- Stay in cooler environment with reduced sweating
- Change clothing to breathable, loosely fitting, clean, dry, cotton
- Avoid lotions (occlusive and may obstruct Sweat Glands)
- Avoid skin irritants and use only products free of perfume and dye
XIII. Prevention
- Avoid Occlusion and excessive heat
- Avoid over-dressing
- Consider cool baths (avoid prolonged exposure due to Hypothermia)
- Stay in cool air conditioned environments
XIV. Complications
- Chronic dermatitis
- May follow more severe Heat Rash
- Secondary Bacterial Skin Infection
- Superinfection, typically from scratching
XV. Resources
- DermNet NZ
XVI. References
- Claudius and Behar in Herbert (2020) EM:Rap 20(8): 5-7
- Salinas and Ruttan (2017) Crit Dec Emerg Med 31(9): 3-10
- Zink (2020) Crit Dec Emerg Med 34(3): 19-27
- Feng (1995) Cutis 55:213-6 [PubMed]
- O'Connor (2008) Am Fam Physician 77:47-52 [PubMed]