Continuum of Light Sensitivity in Atopic Dermatitis: A retrospective analysis of 139 cases in Scotland

Background: Previous reports have characterized photosensitivity in atopic dermatitis (AD), but with differences in terminology and criteria. Objective: This study aims to assess outcomes in 139 patients with AD referred for photodiagnostic testing and to establish diagnostic criteria for photosensitivity in AD. Methods: Clinical and photodiagnostic data were reviewed, categorizing photosensitivity into photoexacerbated AD, photosensitive AD, and chronic actinic dermatitis. Results: Of the patient cohort, the mean age was 42.6 ± 16.7 years, and 61.9% were men. In total, 51.1% of the patients with photoexacerbated AD had normal monochromator phototesting, and 7.9% of the patients with photosensitive AD displayed slight-to-moderate ultraviolet (UV)-A sensitivity (≥30% of normal minimal erythema dose [MED]) and mostly normal or slightly reduced UV-B MEDs (≥80% of normal MED). Conversely, 41% of the patients had chronic actinic dermatitis, and 93% of this group demonstrated significant UV-B sensitivity, with very low UV-B MEDs (<80% of normal MED) and/or very low UV-A MEDs (<30% of normal MED). No significant differences in sex, age, or skin phototype were observed between the groups. Serial phototesting revealed changes in photosensitivity status over time in 8 patients. Limitations: A small sample size and retrospective design. Conclusions: This study highlights the heterogeneity of photosensitivity patterns in patients with AD and the importance of follow-up assessments due to potential shifts in disease spectrum over time.