Treatment with dapsone and minocycline interrupts the eruption of prurigo pigmentosa and stops the pruritus of it, but does nothing to lessen the pigmentation in reticular pattern. Shimizu, in 1985, stated that "a logical explanation of the pharmacologic action of dapsone remains to be found"³³ and Teraki, in 1994,⁹¹ delineated that sentiment when he wrote that the mechanism of action of minocycline and dapsone is "not yet clear." Earlier, in 1992, Sakamoto et al. speculated that their patient with prurigo pigmentosa "responded well to dapsone . . . through supression of the function of neutrophils infiltrating in the early lesion."⁴⁶ No other article about prurigo pigmentosa besides that of Sakamoto et al. addresses the question of why the drugs mentioned supra vide are effective in inhibiting formation of the pruritic red papules that are replete with neutrophils in the papillary dermis and the epidermis of prurigo pigmentosa.

Several dermatitides, such as dermatitis herpetiformis, pemphigus herpetiformis, pustular psoriasis, pyoderma gangrenosum, Sweet's syndrome, and conglobate acne also respond favorably to sulfonamides and dapsone. Those diseases have in common infiltration overwhelmingly by neutrophils. Dapsone is said to inhibit release of lysosomal enzymes from neutrophils⁹⁴ and to hamper generation of oxygene intermediates by neutrophils.⁹⁵

Minocycline is a semisynthetic tetracycline known to possess anti-inflammatory properties. Tetracyclines inhibit chemotaxis of neutrophils^96–98 and have been alleged to be efficacious in various inflammatory disorders, among them, acne vulgaris and pyoderma grangrenosum, those dermatitides being made up of dense infiltrates of neutrophils.

Potassium iodide is effective in treatment of erythema nodosum^99,100 and of Sweet's syndrome,¹⁰¹ an effect posited to be consequent to inhibition of migration of neutrophils¹⁰² or impairment of generation of oxygene intermediates by neutrophils.⁸⁹ Recent studies have shown that macrolide antibiotics inhibit secretion of IL-6 and IL8 and, for that reason, are able to suppress infiltrates of neutrophils in the lung and in the skin.^103–105

A unifying aspect of all medications that have proven to be beneficial to patients with prurigo pigmentosa is capability for inhibiting migration and/or function of neutrophils. At an incipient stage, when neutrophils are preponderant, administration of drugs that have been shown to be impressive may be the way to abort the process of prurigo pigmentosa