Miliaria is caused by occlusion of the epidermal portion of eccrine sweat ducts. Miliaria pustulosa is a miliaria variant that occurs when pustules form in miliaria rubra. These pustules are usually sterile, but occasionally secondary infection with Staphylococcus aureus can occur.

The pathogenesis of miliaria is often related to conditions of high fever or high ambient temperatures with resulting hyperhidrosis, and it is more prevalent in hot, humid conditions and tropical climates. It is a benign disease characterized by intense pruritus and a stinging or "prickly"-type sensation. It is a common phenomenon postoperatively and in bedridden and febrile patients.

Other miliaria variants include the most superficial type, miliaria crystallina, miliaria rubra itself, and miliaria profunda (skin-colored papules with possible associated hypohidrosis or anhidrosis).

Both miliaria rubra and pustulosa have been reported to occur in newborns with type 1 pseudohypoaldosteronism. This typically resolves upon stabilization of disease.