Lactic acid sting test and capsaicin test differentially induce facial erythematous reaction in subjects with sensitive skin

Abstract Background Sensitivity skin (SS) is a common skin disorders, which have a various of clinical manifestation. Facial erythema is common objective symptom of SS. However, the reasons for the occurrence of erythema in sensitive skin are not fully understood. Aims In this study, we preliminarily explain the possible factors inducing erythema of sensitive skin by evaluating facial erythematous reaction to lactic acid sting test (LAST) and capsaicin test (CAT) in subjects with sensitive skin. Methods A total of 197 subjects were divided into five groups, that is, normal controls (NC), LAST‐positive (LAST + ), both LAST and CAT positive (L + C + ), both LAST and CAT negative (L − C − ) and CAT‐positive (CAT + ). Erythema index (EI), a * value, and tissue viability imaging (TIVI) were measured before and after LAST and CAT, The ΔEI, Δ a *, and ΔTIVI before and after LAST and CAT were calculated, and the correlation between the scores of CAT, EI values, a * values, and TIVI values were analyzed to clarify the causes of facial erythema. Results Our results showed that EI values and a * values were significantly higher in the L + C + and CAT + group than in NC group, TIVI values were higher in the L + C + group than in NC group. ΔEI and Δ a * values after LAST did not differ significantly among five groups. However, ΔEI values in L + C + group were higher than that in L − C − group, while Δ a * values were higher in CAT + group than in NC. Moreover, ΔTIVI values in L + C + group and CAT + group were also significantly higher than that in NC group after capsaicin stimulation. CAT scores correlated positively with EI, a * and TIVI values. Conclusion Our results suggest that sensitive skin subjects with positive CAT are more likely to experience erythema reactions, and vasodilation is more pronounced after capsaicin stimulation. Reducing vascular and neural hyperreactivity could be therapeutic target in management of facial erythema in subjects with sensitive skin.