Itch Sensation Induced by Multiple Applications of Pruritogens (temporal Summation)

Not Applicable

Recruiting

• Conditions: Histamine; Cowhage
• Interventions: Other: Histamine; Other: Cowhage

• Registration Number: NCT06328543
• Lead Sponsor: Aalborg University

Brief Summary

In This experiment, the investigators would like to design a new itch model based on the temporal summation of pruritic stimuli. The hypothesis behind this study (temporal summation) is that two overlapped applications of pruritogens will result in a higher itch sensation compared with a single application.

Detailed Description

Chronic itch affects approximately a fifth of the global population and is associated with substantial negative consequences for the affected individuals. Furthermore, there is a lack of efficient treatment options for chronic itch. In order to mimic a clinical itch condition as presented in patients, the aim of the project is to investigate a new itch model based on the multiple applications of pruritogens (temporal summation). In particular, the purpose is to evaluate if a single application of cowhage/histamine (non-histaminergic and histaminergic itch, respectively) results in a lower itch sensation compared with two overlapped applications of the pruritogens on the same area.

Study Timeline

• Study First Submitted: 2024-03-19
• Study First Submitted QC: 2024-03-22
• Study First Posted: 2024-03-25
• Status Verified: 2024-11
• Study Start: 2024-11-01
• Last Update Submitted: 2024-11-20
• Last Update Posted: 2024-11-22
• Primary Completion: 2025-12-31
• Study Completion: 2026-12-31

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 26

Inclusion Criteria

• Healthy men and women
• 18-60 years
• Speak and understand Englis

Exclusion Criteria

• Pregnancy or lactation
• Drug addiction defined as any use of cannabis, opioids, or other addictive drugs
• Previous or current history of neurological (e.g. neuropathy), immunological (e.g. asthma, immune deficiencies, arthritis), musculoskeletal (e.g. muscular pain in the upper extremities,), cardiac disorder, or mental illnesses that may affect the results
• Lack of ability to cooperate
• Current use of medications that may affect the trial such as antihistamines, antipsychotics, and pain killers, as well as systemic or topical steroids
• Skin diseases (e.g. atopic dermatitis, pruritus nodularis, eczema, psoriasis)
• Moles, scars, or tattoos in the area to be treated or tested.
• Consumption of alcohol or painkillers 24 hours before the study days and between these
• Acute or chronic pain
• Participation in other trials within one week of study entry (four weeks in the case of pharmaceutical trials)

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
1st pruritogen	Histamine	The subproject is conducted in 1 session (approx. 3 hours in total) divided into two parts. In the first part, 3 test areas (3x3 cm) will be selected on one forearm of the subject. The 3 areas will be randomly treated with 1 application of cowhage, 2 applications of cowhage (the second application will be conducted 90 seconds after the first one in the same area), and 2 applications of cowhage (the second application will be conducted 180 seconds after the first one in the same area). Itch will be monitored using a VAS (visual analog scale) for 15 min in each session. After the removal of cowhage, FLPI, alloknesis, and mechanically evoked itch will be measured.
2nd pruritogen	Cowhage	The second part will be conducted 20 minutes after the first part, and the procedure will be the same, but using histamine instead of cowhage. The two parts will be randomized between subjects.

Primary Outcome Measures

Name	Time	Method
Assessment of itch	1 minute after every itch inductions	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'.
Assessment of pain	1 minute after every itch inductions	Immediately following the itch provocations, participants will be instructed to rate the pain 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 pain' and 100 'worst pain imaginable'

Secondary Outcome Measures

Name	Time	Method
Microvascular reactivity	10 minutes after every itch inductions	The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging.
Alloknesis	12 minutes after every itch inductions	Alloknesis sensation is measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN.
Mechanically evoked itch	15 minutes after every itch inductions	Mechanically evoked itch is measured using three von Frey filaments of 4.08, 4.16 and 4.31 (1.0, 1.4, 2.0 g, respectively) (North Coast Medical, Gilroy, CA). The center of the skin area is stimulated by 3 pricks, repeated 3 times in short succession. After a total of 9 stimulations, the participants will report the itch elicited on a numerical rating scale (NRS) from 0 to 10 (0 = "no itch"; 10 = "worst imaginable itch").

Trial Locations

Locations (1)

Aalborg University; 🇩🇰 Aalborg, Denmark