With this experiment, we want to use to investigate whether repeated application of EMLA cream as a tool to modulate non-histaminergic itching, which is produced using small needles from the plant mucuna pruriens (it is known that antihistamine does not attenuate this form of itch) and we want to compare the effect of short (1 hour) and prolonged (3 hours) application of EMLA. The sub-project takes place in 3 sessions over a period of 3 consecutive days (24 hours apart). All sessions will be identical.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
22
At the start of each session, the middle forearms of the subject will each be divided into two squared areas (4x4 cm). On each arm, the two areas will be located 4 cm apart. Then one area will be pre-treated with cutaneous 2.5% lidocaine/2.5% prilocaine cream (EMLA cream) for 1 hour.
At the start of each session, the middle forearms of the subject will each be divided into two squared areas (4x4 cm). On each arm, the two areas will be located 4 cm apart. Then one area will be pre-treated with cutaneous 2.5% lidocaine/2.5% prilocaine cream (EMLA cream) for 3 hours.
At the start of each session, the middle forearms of the subject will each be divided into two squared areas (4x4 cm). On each arm, the two areas will be located 4 cm apart. Then two area will be pre-treated with a vehicle cream for 1 h.
Aalborg University
Aalborg, Denmark
Measuring itch intensity 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
Time frame: For 9 minutes
Measuring pain intensity 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".
Time frame: For 9 minutes
Superficial blood perfusion measurement
Superficial blood perfusion is measured by a Speckle contrast imager
Time frame: After 1 hour
Superficial blood perfusion measurement
Superficial blood perfusion is measured by a Speckle contrast imager
Time frame: After 3 hours
Superficial blood perfusion measurement
Superficial blood perfusion is measured by a Speckle contrast imager
Time frame: 10 min after cowhage application
Measuring Alloknesis
Alloknesis sensation is measured using a standardized sensory brush exerting a force of 200 to 400 mN.
Time frame: After 1 hour
Measuring Alloknesis
Alloknesis sensation is measured using a standardized sensory brush exerting a force of 200 to 400 mN.
Time frame: After 3 hours
Measuring Alloknesis
Alloknesis sensation is measured using a standardized sensory brush exerting a force of 200 to 400 mN.
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At the start of each session, the middle forearms of the subject will each be divided into two squared areas (4x4 cm). On each arm, the two areas will be located 4 cm apart. Then two area will be pre-treated with a vehicle cream for 3 h.
Cowhage spicules are 1-2 mm in length and have a diameter of 1-3 μm. The spicules are inserted by gently rubbing 30-35 spicules into a 1 cm diameter skin area.
Time frame: 10 min after cowhage application
Measuring Hyperknesis
Hyperknesis is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 miliNewton of force).
Time frame: After 1 hour
Measuring Hyperknesis
Hyperknesis is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 miliNewton of force).
Time frame: After 3 hours
Measuring Hyperknesis
Hyperknesis is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 miliNewton of force).
Time frame: 10 min after cowhage application
Measuring Erythema
The onset of erythema is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: After 1 hour
Measuring Erythema
The onset of erythema is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: After 3 hours
Measuring Erythema
The onset of erythema is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: 10 min after cowhage application
Measuring Skin Pigmentation
The onset of skin pigmentation is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: After 1 hour
Measuring Skin Pigmentation
The onset of skin pigmentation is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: After 3 hours
Measuring Skin Pigmentation
The onset of skin pigmentation is measured with a spectrometer (ColorMeter, DSM II; Cortex Technology, Hadsund, Denmark).
Time frame: 10 min after cowhage application