A New Model to Induce Itch and Inflammation

Investigating the Neurophysiology of Itch

This project aims to create a reliable, long-lasting itch model by synergistically combining thermal pre-conditioning with the application of histamine or cowhage.

Two areas (4x4 cm, one on each forearm), will be selected. Initially, superficial blood perfusion will be measured in each area, followed by pruritogens application. During the 10 minutes of the application of the pruritogens, itch will be continuously monitored using a VAS scale. After the pruritogens application, assessment of the superficial blood perfusion (SBP), mechanical sensitivity, and thermal sensitivity will be conducted. The session will be identical to the first session, but pre-heat conditioning will be applied prior to pruritogens application.

Inclusion Criteria:

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

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 (e.g., stroke), or psychiatric diagnoses (e.g., depression, bipolar disorders, acute and chronic psychosis) that may affect the results
• Current use of medications that may affect the trial, such as antihistamines, antipsychotics, painkillers, and 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 (forearm/hand).
• Consumption of alcohol or painkillers 24 hours before the study days and between these
• Acute or chronic pain
• Unable to answer the "Transcranial Magnetic Stimulation Adult Safety Screen" (subprojects 2-4)
• Contraindications to transcranial magnetic stimulation (TMS) application (history of epilepsy, metal implants in head or jaw, etc.) (subprojects 2-4)
• Presence of implanted hearing aids or metal implants on the face, including permanent makeup or tattoos (subprojects 2-4)
• Contraindications to capsaicin, including intolerance to chili or burns or wounds at the application sites (subprojects 2, 3, and 4)
• Participation in other trials within one week of study entry (four weeks in the case of pharmaceutical trials)
• The subject is assessed as unable to engage in the necessary cooperation required by the study