Heat Rash

Heat rash, prickly heat and miliaria, are the names of a common condition of the skin. It affects more than 15% of newborns, but can affect in any age and is more frequently in warm countries.

Causes of the Miliaria in its different variants.

  • Crystallina:

Obstruction of the eccrine sweat duct as it courses through the stratum corneum. sweats collects beneath stratum corneum, causing clear, small, flaccid vesicles that often likened to ¨dew drops¨

  • Rubra (prickly heat):

Usually appear after the first week of life, due to a blockage of the sweat ducts, but in a deeper level (the malpighian layer) of the epidermis. The obstructed flows leads to leakage of fluid into the lower epidermis and upper dermis, resulting in an inflamatory response that accounts for the development of erytemathous papules and pustules.

  • Profunda (Rare):

A more inflammatory variant, is related to a deeper obstruction of the eccrine duct and is very rare in infants.

Miliaria Crystallina and Rubra may be seen in relation to excessive warming inside an incubator, overswalddling, fever or oclusive dressing.
Lesion occur most commonly on the forehead, neck and upper trunk as well in areas of covered skin.
In miliaria crystallina, the characteristic histologic features are sub corneal or intra corneal vesicles that are centred on the acrosyringium with relatively little surrounding inflamation.

In Miliaria rubra, intraepidermal spongiosis, vesicles and chronic inflammatory infiltrate in dermis.

Miliaria (Heat Rash)Treatment.


  • Avoid wearing tight clothing and allow your skin to breathe.
  • Do not use thick lotions or creams that can clog your pores.
  • Try not to overheat, in the warmer months look for air conditioning.

Cure: Spontaneous resolution with cooling

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