Pigmented Contact Dermatitis to Cosmetics: A Prospective Observational Study From a Tertiary Care Hospital

Background Pigmented contact dermatitis (PCD) is a pigmentary variant of contact dermatitis characterized by gradually developing facial hyperpigmentation with minimal or absent overt dermatitis. Owing to its close resemblance to other causes of facial melanosis, PCD is frequently underdiagnosed. Patch testing plays a crucial role in identifying causative allergens and guiding avoidance-based management. Objectives To evaluate the clinical profile, dermoscopic features, and patch test allergen spectrum in patients with PCD attending a tertiary care hospital. Methods This prospective observational study was conducted over a period of 1.5 years in the Department of Dermatology, Santosh Medical College and Hospital, Ghaziabad. A total of 55 patients clinically diagnosed with PCD and fulfilling inclusion criteria were enrolled after informed consent. Detailed demographic and clinical data were recorded using a structured proforma. Dermatoscopic examination was performed using a DermLite DL5 dermoscope (DermLite LLC, Aliso Viejo, CA). Patch testing was carried out using the Indian Standard Battery and Indian Cosmetic Series, with readings taken at 48 hours, 96 hours, and on day 7, interpreted according to ICDRG criteria. Statistical analysis was performed using IBM SPSS version 27.0. Results The majority of patients were women (n=41; 74.5%), with the commonest age group being 31-40 years (n=23; 41.8%). Brownish-black pigmentation was the predominant clinical presentation. Dermatoscopy most frequently revealed brownish-gray background pigmentation, brown and gray globules, and follicular plugs with perifollicular white halos. Patch test positivity to at least one allergen was observed in 43 (78.2%) patients. Paraphenylenediamine (n=16; 27.1%) was the most common allergen, followed by cetrimide (n=9; 15.3%) and lavender absolute (n=7; 11.9%). Hair dye was the most frequent exposure source associated with allergen positivity. Conclusion: PCD predominantly affects young to middle-aged females and is strongly associated with cosmetic and hair dye exposure. Patch testing is an essential diagnostic tool for identifying relevant allergens and enabling effective prevention through targeted avoidance.