Dermoscopy of patch test reactions: study of applicability in differential diagnosis between allergic and irritant reactions

Patch test reactions through the lens of dermoscopy: Further insights, particularly on weak allergic reactions

“…Some noninvasive tests have been applied in an attempt to improve diagnostic specificity, including reflectance confocal microscopy, ultrasound, and conventional as well as high‐definition optical coherence tomography . So far, only one previous paper has reported the use of dermoscopy in the assessment of reactions to patch tests . This is rather surprising, as the dermatoscope, unlike other diagnostic devices, is a universal tool, very familiar to dermatologists and available in almost any outpatient setting.…”

“…Table summarizes and compares the dermoscopic features of allergic (all allergic and only weak allergic, ie, + reactions) and irritant patch test reactions (both irritant reactions captured from patients and those induced by SLS in healthy volunteers). Dermoscopy of allergic reactions as a whole, regardless of their clinical scores, was similar to our previous study . Selectively considering the weak allergic reactions, dermoscopic examination demonstrated vesicles in 36 (78.3%) cases, although they were not observable to the naked eye (OR = 323, 95% CI: 18.3‐5701, P < .001).…”

“…Our results confirmed that patch test reactions exhibit characteristic dermoscopic patterns, which significantly differ according to their allergic or irritant nature, as already found (Figure ) . With specific reference to weak (+) allergic reactions, the most noteworthy finding was that they exhibited typical whitish vesicles in most cases (approximately 78%).…”

“…In this observational, cross‐sectional study, we screened for inclusion all consecutive adult outpatients (≥18 years) who were patch tested at the Allergy Unit of the Department of Dermatology of Ferrara during a 6‐month period for suspected allergic contact dermatitis. The patients included during this second phase of the study were added to the previously enrolled population . To assess the dermoscopic features of induced irritant reactions, we patch tested healthy volunteers with sodium lauryl sulfate (SLS), which has been used extensively as positive control for skin irritation tests.…”

“…In a previous study, we described for the first time the main dermoscopic features of patch test reactions . We found that dermoscopic patterns of allergic and irritant patch test reactions differ significantly.…”