Evaluation of Peripheral Itch Mechanisms Following Injection of Morphine

Inclusion Criteria: * Healthy men and women * 18-60 years * Speak and understand English Exclusion Criteria: * Participants with any clinically significant abnormalities that in the opinion of the investigator may increase the risk associated with trial participation or may interfere with the interpretation of the trial results. * Pregnancy or lactation * Drug addiction defined as any use of cannabis, opioids or other addictive drugs * 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. * Participants with known allergy/discomfort to the opioid morphine and antihistamine. * Skin diseases * 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 1 week of study entry (4 weeks in the case of pharmaceutical trials)