TRPA1 and Erythema: At day 5, but not day 3, the total PSI scores of TRPA1 KO mice (P < 0.001) were consistently decreased in TRPA1 KO (vs WT) mice, which were reflected in individual scores of scales (PSI‐S) (P < 0.01), induration (PSI‐I) (P < 0.001) and erythema (PSI‐E) (P < 0.05) (Figure 2B).