miliaria rubra

Last reviewed 06/2022

Miliaria rubra, also known as prickly heat or heat rash, occurs in susceptible persons as a result of eccrine sweat duct occlusion

Miliaria rubra are tiny red itchy papules which occur as a result of exposure to heat.

It is a response to sweat from rupture or plugging of the sweat ducts (1):

  • small, diffuse papules and vesicles with surrounding confluent erythema appear suddenly in occluded areas during sweating, such as with physical exertion
  • there is no follicular association, and patients may describe a 'prickly' sensation
  • typically lesions are concentrated on the face, upper trunk, and the neck, it may also be seen on extremities

Click here for an example image of this condition

Polymorphic light eruption is included in the differential diagnosis of this condition.


  • 1) Acne, rosacea, and related disorders. In: Habif TP. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 4th ed. Philadelphia, Pa.: Mosby; 2004:205