Are Patch Testing Reactions Underrecognized in Skin of Color? Evaluating the Frequency of Borderline Reactions by Fitzpatrick Skin Type

<u><b><i></i></b> <b><i>Background:</i></b></u> Patch testing reactions can be difficult to interpret in patients with skin of color (higher Fitzpatrick skin types [FSTs]) due to limited erythema or vesiculation. Missed reactions may lead to prolonged allergic contact dermatitis duration and prevent disease clearance in this population. <u><b><i>Objective:</i></b></u> To compare the frequency of borderline patch test reactions in patients with different FSTs (I, II, III, IV, V, VI). <u><b><i>Methods:</i></b></u> Retrospective study of 1899 patients comprehensively patch tested in a major metropolitan area over a 4-year period. Borderline (doubtful, ±) reaction frequency and patient FST were recorded and used for analysis. <u><b><i>Results:</i></b></u> There were statistically significant differences in the frequency of borderline reactions between FSTs I/II and V/VI (<i>P</i> < 0.0001) and across all 6 FSTs (<i>P</i> < 0.0001). Patients with FST V or VI had 43% lower odds of having a borderline reaction (OR: 0.57, 95% CI: 0.47-0.69) compared with patients with FST I or II. Patients with FST VI showed the lowest proportion of borderline reactions. <u><b><i>Conclusions:</i></b></u> Among patients with skin of color, borderline reactions are diagnosed less commonly and may be missed. This has the potential to prolong dermatitis symptoms and prevent disease clearance.