Miliaria
Last Updated: 2023-10-12
Author(s): Steybe T., Navarini A.A.
ICD11: L74.3
Last Updated: 2023-10-12
Author(s): Steybe T., Navarini A.A.
ICD11: L74.3
Dermatitis hidrotica; Dew drops; Hidroa; Heat flares; Heat pimples; Prickle heats; Red dog; Sweat blisters; Sweat frizzles; Sweat blisters
Miliaria is a common, usually pruritic exanthema caused by obstruction or autoinflammatory processes of eccrine sweat glands and their ducts.
Although miliaria affects all age groups and both sexes equally, infants and children are more at risk due to the immaturity of the excretory ducts. Sweating is the most common risk factor for miliaria. Therefore, hot or humid environments and the presence of fever are associated with miliaria. Miliaria cristallina occurs in 4.5% to 9% of newborns and may also occur in adults who have recently moved to a warmer climate. Miliaria rubra, the most common form of miliaria, often occurs in newborns between 1 and 3 weeks of age. It can also affect up to 30% of adults living in hot and humid areas.
Depending on the pathophysiological point of attack, miliaria can be subdivided according to clinical aspects into:
The main cause of miliaria is occlusion of the eccrine sweat glands or ducts. This can be caused by cutaneous debris or bacteria such as Staphylococcus epidermidis with a biofilm formation. This leads to leakage of sweat into the epidermis or dermis, resulting in cellular hyperhydration, swelling and further obstruction of the excretory ducts. If the eccrine glands or excretory ducts are more severely affected, they may rupture.
Causes of miliaria are:
s.o.
Clinical diagnosis. Dermoscopy has proven to be a useful tool, especially in people with pigmented skin, as it usually reveals large white papules with surrounding halos (white bullseye)
Trunk, rarely extremities. Face, palms and feet mostly omitted.
The histology of miliaria differs according to type, as it is classified according to the depth of occlusion of the eccrine duct. Miliaria cristallina shows subcorneal or intracorneal vesicles from the intraepidermal part of the duct and may contain neutrophils. Miliaria rubra shows epidermal spongiosis with parakeratosis and vesicles in the epidermis communicating with the eccrine duct. It may be associated with an inflammatory lymphocytic infiltrate surrounding the ductus and superficial vasculature. Miliaria profunda involves intradermal spongiosis of the eccrine duct and is similar to miliaria rubra. Miliaria profunda differs from miliaria rubra by further rupture of the eccrine ducts and more severe lymphocytic inflammation. It is periodic acid-Schiff (PAS)-positive and microscopically diastase-resistant.
General measures to reduce sweating and blockage of the eccrine excretory ducts are warranted in the treatment of miliaria. These include cooler environments, wearing breathable clothing, peeling the skin, removing skin-clogging items such as bandages or plasters, and treating febrile illnesses.
The specific modalities for treating miliaria vary depending on the type. Miliaria cristallina is usually not treated as it is self-limited and usually resolves within 24 hours. Treatment of miliaria rubra aims to reduce inflammation, so mild to moderate corticosteroids such as triamcinolone 0.1% cream may be used for one to two weeks. If miliaria pustulosa develops, topical antibiotics such as clindamycin are indicated to treat the overlying bacterial infection.
