Dear Editor, Allergic contact dermatitis (ACD) is a delayed-type hypersensitivity reaction mediated by T cells.1 Patch testing remains the gold standard for identifying allergens. Given limited literature comparing ACD across age groups, we analysed epidemiological patterns, allergen profiles, and patch test positivity in adults (18–64 years) and geriatric patients (≥65 years). A retrospective analysis was conducted on 464 patients attending the dermatology outpatient department of a Tertiary Care Centre. All had clinically diagnosed ACD. Patch testing was performed using the Indian Standard Series (Contact and Occupational Dermatoses Forum of India-approved), once active lesions resolved. Test chambers (aluminium) containing allergens in petrolatum (0.5%–100%) were applied for 48 hours. Readings were recorded at 48 hours, 96 hours, and Day 7. Patients discontinued systemic corticosteroids and antihistamines prior to testing. Data were analysed using SPSS Version 18.0. Of the 464 patients, 342 (74%) showed positive patch test reactions—304 adults (89%) and 38 geriatric patients (11%). Male preponderance was noted: 53.9% in adults and 76.3% in the elderly. Hand-foot eczema predominated in adults, whereas localized eczema, especially scalp involvement due to the hair dye, was more common in geriatrics. The most frequent adult allergens were potassium dichromate, nickel sulphate, and para-phenylenediamine (PPD). In the geriatric group, PPD, potassium dichromate, and neomycin sulphate were most common. Polysensitization was more prevalent in adults, involving combinations like potassium dichromate + nickel sulphate and mercaptomix + Mercaptobenzothiazole. Geriatrics showed fewer polysensitivities, often involving medicament-related allergens Table 1.Table 1: Distribution and allergen pattern of allergic contact dermatitis among adults and geriatricsThis study reveals a distinct age-related variance in allergen sensitivity and patch test positivity, with geriatric patients exhibiting a lower reactivity rate. Immunosenescence—marked by reduced T-cell responsiveness, diminished Langerhans cell density, impaired cytokine production, and decreased antigen presentation—may explain attenuated responses in older individuals.2,3 Chronic illnesses and polypharmacy further contribute to the immune suppression.2,3 Our overall positivity rate of 74% exceeds those reported in Sri Lanka (55%)4 and by Kasumagic-Halilovic and Ovcina-Kurtovic (62%).5 However, low positivity found may be due to latent sensitization in asymptomatic elderly patients, highlighting the complexity of geriatric immune responses. Scalp involvement was frequently observed in older adults, likely linked to increased PPD exposure from hair dyes. These findings parallel those of Lee et al.,6 who noted PPD, nickel, and cobalt as major allergens in adult Korean populations. Occupational factors likely influenced adult sensitization—especially among those in construction, leather, and automotive sectors where chromium and nickel exposure are high.2 In contrast, geriatric sensitization skewed toward medicament-related allergens (e.g., neomycin, lanolin), reflecting chronic disease management and reduced exposure to industrial or cosmetic agents. This is consistent with observations by Tosti et al. and Lee et al., who reported lower sensitivity to metal allergens and heightened sensitivity to therapeutic agents in older adults.2,6 Extended patch test reading—particularly Day 7—is crucial in elderly patients due to delayed hypersensitivity responses.7 Piaserico et al.7 emphasized that late-phase responses may otherwise be missed. Customizing patch series to include medicament and age-relevant allergens like lanolin and neomycin enhances detection in geriatrics.2,3 Comprehensive drug histories are equally vital to avoid false negatives. International studies reflect regional differences. Németh et al.8 noted benzoic acid, methylisothiazolinone, wood tar, and balsam of Peru among top allergens in older Hungarian patients, underscoring the role of geographic and demographic variables. The high rate of PPD sensitization in our elderly group likely reflects evolving cosmetic practices, increased life expectancy, and sustained use of hair dyes. Despite lower ACD prevalence in geriatrics, the morbidity impact remains significant due to diagnostic challenges, chronicity, and co-morbidities. Diagnostic accuracy can be enhanced by tailored allergen panels, longer patch test reading intervals, and consideration of age-related immunological changes. Patch test positivity is significantly lower in the elderly due to age-related immune changes and reduced allergen exposure. However, sensitization to therapeutic agents is comparatively higher, emphasizing the need for customized testing strategies in this population. Understanding these differences is the critical for accurate diagnosis, targeted treatment, and effective prevention strategies across age groups. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Kumar et al. (Fri,) studied this question.