Scalp Allergic Contact Dermatitis: A Retrospective Analysis of Allergen Profiles and Distribution Patterns

Area of Science:

• Dermatology
• Allergology
• Epidemiology

Background:

• Scalp allergic contact dermatitis (ACD) is understudied and often misdiagnosed due to overlapping skin conditions.
• This study aimed to characterize the epidemiology, clinical presentation, and allergen profile of scalp ACD.

Purpose of the Study:

• To investigate the epidemiological and clinical characteristics of scalp ACD.
• To identify common allergens and patterns associated with scalp ACD.
• To explore the impact of preexisting scalp conditions on scalp ACD presentation.

Main Methods:

• Retrospective cohort study of patients with patch test-confirmed scalp ACD from 2009-2023.
• Patients were categorized based on symptoms and presence of preexisting scalp disorders.
• Analysis of demographic, clinical, and patch test data.

Main Results:

• Scalp ACD constituted 3.2% of patch test referrals, predominantly affecting females (91.1%) with a mean age of 50.
• Common symptoms included itching and hair shedding; erythema and scaling were frequent signs. Lesions extended beyond the scalp in 55% of cases.
• Diagnosis delay averaged 17 months, with frequent polysensitization (50.5%) and common allergens including nickel sulfate, paraphenylenediamine, and methylisothiazolinone/methylchloroisothiazolinone.

Conclusions:

• Scalp ACD primarily affects middle-aged women, often presenting with symptoms beyond the scalp and experiencing diagnostic delays.
• Distinct allergen patterns and frequent polysensitization necessitate targeted allergen avoidance strategies.
• Preexisting scalp conditions influence the presentation and management of scalp ACD.