About this trial
The experiment consists of three experimental sessions conducted on three consecutive days.
In all experimental sessions, 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.
In the first session, we will mark six test areas in your face (three on each side on jaw, cheek, and temple, respectively). Thent a series of measure-ments in each test area will be conducted:measurement of the blood flow in the skin and sensitivity tests to pressure, pinprick and stroke with a brush.
In the second session, histamine will be applied in one side of the face. On the other side, cowhage spicules will be applied. After 10 minutes, all the tests will be conducted again.
The third session will be identical to the second. However, instead of histamine and spicules, patches containing capsaicin will be applied. In the other side, we will apply patches with placebo (i.e., a non-active patch). After 20 minutes all the tests will be conducted again.
Eligibility criteria
This trial accepts healthy volunteersQualifiers
Healthy men and women
18-60 years
Speak and understand English
Disqualifiers
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
Trial design
Single group
Treatments tested in this trial
Histamine
Other interventionTo deliver histamine, standard allergy skin prick test (SPT) lancets are applied
Cowhage
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
Capsaicin 8% Patch
Other interventionCapsaicin patches (dosage form: transdermal patch 8% Qutenza, Astellas) will be applied on 3 squared areas in the face.
Demo patch
Other interventionPlacebo patch (demo patch, containing the same formulation as the active treatment with the exception of capsaicin) will be applied on 3 squared areas in the face.
Treatment groups
Trial outcomes
Primary outcomes
Measuring pain by computerized Visual Analog Scale Scoring
We 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
We 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".
Measuring pain by computerized Visual Analog Scale Scoring
We 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
We 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".
Secondary outcomes
Superficial blood perfusion
Superficial blood perfusion (SBP) is measured by a Speckle contrast imager
Superficial blood perfusion
Superficial blood perfusion (SBP) is measured by a Speckle contrast imager
Alloknesis
Measured using a standardized sensory brush exerting a force of 200 to 400 mN.
Alloknesis
Measured using a standardized sensory brush exerting a force of 200 to 400 mN.
Sponsors and contacts
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