The study consists of one experimental session of approximately 1½ hours. The participant will fill in a series of questionnaires about how you perceive itch and pain, and about some traits of your personality, such as depression, anxiety and stress. Afterwards, three areas will be selected on each forearm of the subjects.
Two areas will be treated with histamine, two with cowhage, and two with vehicle. One application of each substance will be conducted including the contagious itch component. During the 10 minutes of the application of the pruritogens, itch and pain will be continuously monitored using a VAS scale.
18-60 years
Speak and understand English
Pregnancy or lactation
Drug addiction defined as any use of cannabis, opioids, or other drugs
Previous or current history of neurological, immunological, musculoskeletal, cardiac disorder or psychiatric diagnoses that may affect the results (e.g., neuropathy, muscular pain in the upper extremities, anxiety, depression, schizophrenia, etc.)
Moles, wounds, scars, or tattoos in the area to be treated or tested
Single group
Histamine
Other interventionTo deliver histamine, standard allergy skin prick test (SPT) lancets are applied
Cowhage (Mucuna Pruriens)
Other interventionThe spicules will be manually inserted. Approximately 30-35 spicules are gently rubbed into a 1 cm diameter skin area on the forearm/face
Placebo
Other interventionTo deliver steril water, standard allergy skin prick test (SPT) lancets are applied
Measuring pain by computerized Visual Analog Scale Scoring
The investigators will ask the subjects to rate the sensation of pain on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates" no pain" and 100 indicates "worst pain imaginable".
Measuring itch by computerized Visual Analog Scale Scoring
The investigators will ask the subjects to rate the sensation of itch on a 100 mm VAS scale ranging from 0 to 100 where 0 indicates "no itch" and 100 indicates "worst itch imaginable".
Pain Catastrophizing Scale (PCS).
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).
Itch Catastrophizing Scale (ICS)
The ICS assesses negative and exaggerated coping concerning anticipated or experienced itchy 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).
Learned Helplessness Scale (LHS)
The questionnaire consists of 20 items, and the participant's response to each item is rated on a 4-point Likert scale ranging from strongly agree (1) to strongly disagree (4).
Depression, Anxiety, Stress Scale (DASS-21)
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"
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