Prurigo pigmentosa
Prurigo pigmentosa is a rare skin condition of unknown cause, characterized by the sudden onset of erythematous papules that leave a reticulated hyperpigmentation when they heal.  The condition is sometimes caused by a recent diet restriction.

  • It is characterized by a recurrent itchy rash with net-like hyperpigmentation.
  • Typical Prurigo pigmentosa
  • It may also occur after a recent rapid weight loss.
References Prurigo Pigmentosa 38261670 
Prurigo pigmentosa, also known as Nagashima disease or keto rash, is a rare inflammatory skin disease initially described by Nagashima et al in 1971. Prurigo pigmentosa typically, but not exclusively, affects young females of East Asian ethnicity, presenting as a symmetrical eruption of urticarial papules on the neck, chest, and back. The papular eruption typically coalesces into a reticulated pattern that repeatedly resolves and recurs, resulting in hyperpigmented skin of cosmetic concern. Prurigo pigmentosa can be triggered by metabolic derangements, including those secondary to ketogenic diets, which have experienced a rise in popularity in recent years.
 Prurigo pigmentosa: A multi-institutional retrospective study 37001731
Prurigo pigmentosa is a skin condition causing sudden, itchy, red bumps in a net-like pattern followed by dark spots. Lately, some evidences were founded that Prurigo pigmentosa is associated with the ketogenic diet. It can affect people of different ages and genders, with a tendency to be more common in females. In cases where returning to a regular diet or using skin treatments doesn't fully help, doctors may prescribe a course of oral antibiotics like doxycycline or minocycline (100 mg twice daily for 1 to 2 months).