In the first session, the subjects will fill some questionnaires. After that, a squared area of 4x4 cm will be selected at the center of each middle forearm of the subject and cowage or histamine will be applied for 10 minutes, during which the pain/itch following the cowhage/histamine application will be monitored with a VAS scale. After the itch-induction, the subjects will fill in other questionnaire. In second session, the subjects will fill some questionnaires. After that, a squared area of 4x4 cm will be selected at the center of each middle forearm of the subject and cowage or histamine will be applied for 10 minutes, during which the pain/itch following the cowhage/histamine application will be monitored with a VAS scale. After the itch-induction, the subjects will fill out other questionnaires. The order will be randomized, so if the subjects were given the cowhage in the first session, they will receive the histamine application in the second session, and vice versa.

In the first session, the subjects will fill some questionnaires. After that, a squared area of 4x4 cm will be selected at the center of each middle forearm of the subject and cowage or histamine will be applied for 10 minutes, during which the pain/itch following the cowhage/histamine application will be monitored with a VAS scale. After the itch-induction, the subjects will fill in other questionnaire. In second session, the subjects will fill some questionnaires. After that, a squared area of 4x4 cm will be selected at the center of each middle forearm of the subject and cowage or histamine will be applied for 10 minutes, during which the pain/itch following the cowhage/histamine application will be monitored with a VAS scale. After the itch-induction, the subjects will fill out other questionnaires. The order will be randomized, so if the subjects were given the cowhage in the first session, they will receive the histamine application in the second session, and vice versa.

Histaminergic itch will be evoked by a 1% histamine solution. A droplet of histamine solution will be placed on the predetermined area on the forearm, and the SPT lancet will be pierced through the histamine with 120 g of pressure for 1-2 seconds.

The Reinforcement Sensitivity Theory - Personality Questionnaire contains the following subscales: the Fight-Flight-Freeze System (FFFS, 10 items); the Behavioral Inhibition System (BIS, 23 items); and the Behavioral Approach System (BAS, 32 items). In total, 65 items have to be answered on a 4-point Likert-type scale ranging from 1 (not at all) to 4 (Highly).

The PSQI consists of 19 items generating seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction. The seven component scores can be summarized in a global score ranging from zero to 21 with higher scores reflecting a worse overall quality of sleep.

The questionnaire measures the magnitude of depression, anxiety, and stress. Each of these three subscales consists of 7 questions answered using a 0-3 Likert scale, with 0 meaning "it did not apply to me", and 3 meaning "it applied to me very much"

PANAS measures positive and negative affect dimensions. Positive affects (PA) are defined as "the extent to which a person feels active, enthusiastic, and alert". Negative affect (NA) is a condition of "general distress and unpleasable engagement".

The PCS assesses negative and exaggerated coping concerning anticipated or experienced painful stimuli. Thirteen items have to be answered on a 5-point Likert-type scale ranging from 0 (Not at all) to 4 (all the time).

Immediately following the itch provocations, participants will be instructed to rate the itch intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no itch' and 100 'worst itch imaginable'.