Miliaria is a disorder of eccrine sweat retention caused by obstruction of the sweat duct at different levels within the epidermis or dermis. It presents as vesicles, papules or pustules and is classified into crystallina, rubra and profunda according to the depth of duct blockage. The lesions are non-follicular and typically appear on occluded skin areas during hot or humid conditions.
What are the characteristics of miliaria?
Miliaria is recognised by superficial vesicles, papules or pustules that are non-follicular and arise in areas of high eccrine density. Miliaria crystallina presents as 1–2 mm thin-roofed vesicles filled with clear fluid, usually grouped on the head, neck or upper trunk; the lesions rupture easily and leave fine branny scale . Miliaria rubra produces 2–4 mm erythematous papules or papulovesicles on a background of erythema, accompanied by pruritus or stinging; distribution is typically the trunk, neck and flexures in adults, and the axillae, groin or neck folds in infants . Miliaria pustulosa is a variant of rubra in which sterile pustules develop within the papules. Miliaria profunda forms 1–3 mm firm, flesh-coloured papules that are asymptomatic and located on the trunk or extremities; affected skin shows reduced or absent sweating, and recurrence after exercise is common.
Why does miliaria develop?
Miliaria results from obstruction of the eccrine sweat duct, most often at the stratum corneum or the mid-epidermis. The earliest change is the accumulation of PAS-positive, diastase-resistant material within the distal duct lumen; this plug is composed of compacted keratin, lipid-depleted corneocytes, and biofilm-forming bacteria such as Staphylococcus epidermidis. Once the lumen is narrowed, sweat accumulates proximal to the obstruction, producing overhydration and pressure that distend the duct and eventually rupture it, releasing sweat into the surrounding epidermis or dermis.
Individuals at highest risk are those who sweat excessively while the skin is occluded or over-hydrated. Neonates and preterm infants are especially vulnerable because eccrine ducts remain underdeveloped; duct patency is usually achieved only after 36 weeks’ gestation, and premature neonates may require an additional 1–2 weeks of post-natal maturation before efficient sweating begins. Any condition that increases sweat output—high fever, strenuous exercise, cholinergic drugs (bethanechol, clonidine, neostigmine), or isotretinoin therapy.
Occupational and environmental factors further determine susceptibility: outdoor workers, and athletes wearing flame-resistant or synthetic uniforms in hot environments have been documented to develop miliaria rubra or profunda, particularly under garments that trap moisture and raise local skin pH above 8.8. Occlusive transdermal patches, tight dressings, or prolonged use of radiant warmers in neonatal intensive care units also create the combination of heat, humidity, and mechanical occlusion required for duct blockage.
How does miliaria appear on dermoscopy?
With a polarised IBOOLO dermatoscope, crystallina shows clear, thin-roofed vesicles that collapse on pressure; rubra displays erythematous papules with central white globules surrounded by darker halos (“white bullseye”); profunda yields flesh-coloured papules with absent surface vessels and surrounding subtle perilesional pallor. These patterns allow differentiation from folliculitis, candidiasis or viral exanthems.
What new products has IBOOLO Dermatoscope recently launched?
IBOOLO has released the new dermatoscope DE-500. It features an upgraded lens that delivers excellent image quality. The scale lines are now laser-etched for greater clarity and durability, replacing the previous silk-print method used in the pocket series. A UV light mode has been added, expanding the range of lesions that can be examined to include fungal lesions and pigment-deficiency disorders. For attachment, the DE-500 replaces the threaded interface with an innovative rear magnetic disc that snaps onto the phone instantly.
Next month, a new dermatoscope accessory will launch: a single-use infection-control contact. Its core function is to create a sterile barrier between the dermatoscope and the patient’s skin, preventing cross-contamination by pathogens via the lens or the operator’s hands during the examination. After each use, the shield is discarded, eliminating the need for repeated disinfection. The transparent film does not affect optical imaging, ensuring diagnostic accuracy.
How to effectively treat miliaria?
Effective management is based on two simultaneous actions: eliminating the environmental triggers that sustain duct obstruction and applying targeted therapy according to the type of lesion. Remove heat and humidity first: move the patient to an air-conditioned or shaded area, loosen or remove occlusive clothing, and discontinue any topical ointments that trap sweat. Cool showers or lukewarm compresses reduce surface temperature and help clear residual sweat without causing rebound vasoconstriction.
Miliaria crystallina is self-limiting and usually requires no pharmacologic intervention beyond cooling; lesions clear within 24 hours once sweating is controlled.
Miliaria rubra benefits from a short course of a mild- to moderate-potency topical corticosteroid (e.g., 0.1 % triamcinolone cream once daily for 7–14 days) to suppress periductal inflammation. If pustules indicate secondary bacterial colonisation, clindamycin 1 % lotion or gel applied twice daily for 5–7 days is adequate.
Throughout treatment, advise lightweight clothing, frequent skin inspection, and prompt washing after sweating to prevent recurrence.