Procedure and statistical methods

Average capsaicin sensitivity (sensitivity defined as detected concentration) were calculated by using the number of the concentration (numbers 1–6 in Table Table1)1) that each participant reacted to. Comparisons of capsaicin sensitivity between participants with and without different skin symptoms were performed using the Mann–Whitney U-test (Table (Table22).

Denotation of sensitivity, number, sex and age (years) of participants that reacted to each concentration of capsaicin

Comparison of detected concentration groups for capsaicin for participants reporting a symptom often or sometimes with those not having the symptom during the last month (number of participants within brackets)

Sensitivity for groups is compared with Mann–Whitney U-test

*p < 0.05

Based on their sensitivity to capsaicin, the participants were divided into three groups. Those who did not react or reacted to 3.16 × 10–3% were considered to have low sensitivity. Those who reacted to 1 × 10–3 or 3.16 × 10–4% medium sensitivity and those who reacted to 1 × 10–4 or 3.16 × 10–5% were considered to have high sensitivity. Differences in PSS and SMBQ between the three groups were compared by one-way analyses of variance (ANOVA) followed by post hoc Tukey’s HSD-test. The level of significance was set to p = 0.05.

Comparisons of PSS and SMBQ for men/women and new/former patients were performed by t test. For statistical calculations IBM SPSS Statistics for Windows, Version 25.0. IBM Corp. Released 2017. Armonk, NY, was used.