Hyperkeratotic flexural erythema (more commonly known as granular parakeratosis) with use of laundry sanitizers containing benzalkonium chloride

Background Hyperkeratotic flexural erythema (HKFE), also known as granular parakeratosis, is a scaly, erythematous or brown eruption, which usually occurs in the intertriginous and flexural areas. It has been linked to the use of benzalkonium chloride (BAK). Aim To review the clinical presentation of patients diagnosed with HKFE who had been exposed to laundry sanitizer containing BAK, and the therapies trialled to treat these patients. Methods This was a retrospective cases series of 45 patients seen by dermatologists in Victoria, Australia. Information was collected on clinical presentation, investigation and management. Results The patients varied in age from 18 months to 89 years. The rash typically presented as a symmetrical erythema with characteristic multilayered brownish epidermal scaling. The most common location of the rash was the inguinal/anogenital area (32 of 45 patients; 71.1%) and there was a female predominance. Regarding treatment, topical corticosteroids were frequently prescribed and antibiotics were trialled in 11 patients; however, the condition resolved spontaneously over time in all patients with use of emollients, along with cleaning of the washing machine by running an empty wash, and repeated washing or sometimes disposal of BAK-contaminated clothing. Conclusion This large case series highlighted the characteristic clinical presentation of HKFE in the setting of BAK used in laundry sanitizer, demonstrating a potential causal link. Further studies are required to evaluate the role of the skin microbiome.