In 1965, Ise and Ofuji described a 42-year-old Japanese housewife with a possible follicular variant of subcorneal pustular dermatosis.  The patient had crops of follicular pustules on her back, face, chest, and upper arms representing histologic subcorneal pustulosis of the upper hair follicles as depicted below. The patient also had a leukocytosis of 14,100 white cells/µL, 8% of which were eosinophils. In 1970, Ofuji et al described 3 additional patients and proposed that this new entity be called eosinophilic pustular folliculitis (EPF).  The use of the term folliculitis has been challenged for this disorder because hair follicles are not seen on the palms or the soles, which may be affected.
Three variants of this disorder have been described: classic eosinophilic pustular folliculitis (as originally described by Ofuji), HIV-associated eosinophilic pustular folliculitis, and infantile eosinophilic pustular folliculitis. Some investigators prefer to consider these 3 distinct disorders. Of the 3, the infantile variety is by far the least characterized. Because the exact nature of these conditions is unknown, whether these conditions are 3 interrelated forms of a single disease or 3 distinct dermatoses is unclear. These conditions share a common pathologic feature, namely a noninfectious eosinophilic infiltration of the hair follicles.
A histologic resemblance exists between eosinophilic pustular folliculitis and fungal folliculitis. Some investigators have speculated that eosinophilic pustular folliculitis is due to hyperreactivity to dermatophytes or saprophytic fungi, such as Pityrosporum ovale, in association with a disordered immune system. This concept is supported by the favorable therapeutic response of some patients to oral itraconazole therapy.
The follicle mite, Demodex, has also been considered a possible triggering agent. In certain patients, a combination of Pityrosporum species and Demodex species might play a role in the pathogenesis of the disease. An aberrant helper T-cell type 2 immune response to a follicular antigen, such as Demodex, might be involved in the pathogenesis of HIV-associated eosinophilic pustular folliculitis (see the image below). Eosinophilic pustular folliculitis has been described in atopic children  with hypersensitivity to Dermatophagoides pteronyssinus. Some authorities have suggested that patients with eosinophilic pustular folliculitis shoud be screened for the presence of coexisting Th2-mediated disorders. 
An anaerobic organism similar in morphology to Leptotrichia buccalis has been found in one biopsy specimen of a patient with HIV-associated Ofuji disease; the disease responded to oral metronidazole. Others believe that at least the HIV-associated form is an autoimmune disorder with the sebaceous gland cell or a constituent of sebum serving as an autoantigen.
A single case has been reported of a patient with Ofuji disease with pemphiguslike antibody detected by direct immunofluorescence on both lesional skin and healthy skin and by indirect immunofluorescence on human skin but not on guinea pig esophagus.  Yet another patient with Ofuji disease and high titers of circulating immunoglobulin G and immunoglobulin M antibodies to the cytoplasm of the basal cells of the epidermis and the outer sheath of hair follicles has also been described. 
Another theory is that eosinophilic chemotactic factors from skin surface lipids may be involved.  A selective migration of leukocyte factor antigen-1–positive eosinophils and lymphocytes to hair follicles may be explained by intercellular adhesion molecule-1 expression by keratinocytes on follicular epithelium but not on epidermis. The expression of endothelial-leukocyte adhesion molecule-1 and vascular cell adhesion molecule-1 by vascular endothelium around hair follicles may also explain this migration.
Eosinophils infiltrating into the dermis and the follicular epidermis express neuronal nitric oxide synthase.  Activated eosinophils release major basic protein with subsequent tissue damage. In addition to degranulating eosinophils, degranulating mast cells are present in the skin of most patients with HIV-associated eosinophilic folliculitis, which suggests a role for both of these cell types in the pathogenesis of this disease.
This is an uncommon disorder, except in the AIDS population. The peak incidence of the classic disease is in the second to fourth decades. The peak incidence is usually in the first year of life for the infantile form; eosinophilic pustular folliculitis may be congenital in infantile cases. It may be seen at any age with HIV disease, with an incidence of almost 10% in one survey. Eosinophilic pustular folliculitis is most frequent in association with a low CD4 count.
All races are affected. The classic form described by Ofuji mainly occurs in Japanese people in Japan. HIV infection is the most common medical condition associated with eosinophilic pustular folliculitis, at least in whites.
Eosinophilic pustular folliculitis is more common in men than in women, although a survey confirmed these data for all but classic eosinophilic pustular folliculitis cases, in which the incidence was the same in both sexes.  With HIV disease, an overwhelming male prevalence exists.
Even in infants, the disease occurs more often in boys than in girls.
A male predominance was observed in those with extrafacial eosinophilic pustular folliculitis, with the immunosuppression-associated type more common among them. 
The main morbidity is chronic persistent pruritus, which, especially in the HIV-related form, can interfere with activities of daily living.
Unfortunately, the classic/Japanese form of this condition usually continues for years with recurrent relapses and remissions. Some patients have achieved long-lasting remissions with indomethacin alone or in combination with dapsone.
Patients with HIV-associated disease may benefit from highly active antiretroviral therapy. Treatment that restores immunity in individuals with HIV infection may clear their skin lesions, which otherwise are chronic and persistent. In the absence of improvement of the underlying immunodeficiency, HIV-associated eosinophilic folliculitis usually does not respond to any treatment; even with ultraviolet B and psoralen plus ultraviolet A phototherapy, the skin lesions recur on discontinuation of phototherapy.
Eosinophilic pustulosis of the scalp in infancy/childhood is a self-limited, albeit recurrent, dermatosis that can be relieved by topical corticosteroids.