Background: 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.
Objective: To compare the frequency of borderline patch test reactions in patients with different FSTs (I, II, III, IV, V, VI).
Methods: 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. Results: There were statistically significant differences in the frequency of borderline reactions between FSTs I/II and V/VI (P < 0.0001) and across all 6 FSTs (P < 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.
Conclusions: 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.