RecruitingNot ApplicableNCT07122973

Topographical Distribution of Itch and Pain Receptors

Pain and Itch Neuromodulation: Effects of Offset Analgesia, Placebo, and Nocebo and Topographical Distribution of Itch and Pain Receptors

Sponsor

Aalborg University

Enrollment

30 participants

Start Date

Sep 17, 2025

Study Type

INTERVENTIONAL

Conditions

Pain Itch

Summary

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

Min Age: 18 YearsMax Age: 60 Years

Inclusion Criteria3

Healthy men and women
-60 years
Speak and understand English

Exclusion Criteria11

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
Current use of medications that may affect the trial such as antihistamines and pain killers
Skin diseases
Consumption of alcohol or painkillers 24 hours before the study days and between these
Acute or chronic pain and itch
Participation in other trials within 1 week of study entry (4 weeks in the case of pharmaceutical studies)
Contraindications to capsaicin, including intolerance to chili or burns or wounds at the application site
The subject is assessed as unable to engage in the necessary cooperation required by the study

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Interventions

OTHERHistamine

To deliver histamine, standard allergy skin prick test (SPT) lancets are applied

OTHERCowhage

The spicules will be manually inserted. Approximately 30-35 spicules are gently rubbed into a 1 cm diameter skin area on the forearm/face

OTHERCapsaicin 8% Patch

Capsaicin patches (dosage form: transdermal patch 8% Qutenza, Astellas) will be applied on 3 squared areas in the face.

OTHERDemo patch

Placebo 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.