Fig. 4.  Stimulus-response functions for pinpricks and tactile stimuli. (A  and C ) Dynamic mechanical allodynia did not develop after incision. Cotton wisp (cw) 3 mN, Q-tip (qt) 100 mN, brush (br) 400 mN. (B ) In contrast, experimental skin incision resulted in mechanical pinprick hyperalgesia. The stimulus-response (S/R-) function for pinprick probes was approximately linear in log-log coordinates in normal skin (blue  squares, blue regression lines). One hour after incision, there was a significant parallel upward shift by 91% of the S/R-function adjacent to the site of incision relative to the baseline (ANOVA (pre vs . post) F^1,19= 21.18, P < 0.001) (red squares). There was no change of the S/R-function at the uninjured control site (D ). Mean ± SEM values across 20 subjects at baseline and 1 h after incision. Each data point represents average pain ratings on a 0–100 numeric ratings scale. A value of 0.1 corresponds to zero pain ratings because a small constant (0.1) had to be added before logarithmic transformation. Asterisk =P < 0.05, triple asterisk =P < 0.001 (post hoc  Scheffé F test) before versus  after incision.