The purpose of this human experimental study is to evaluate the pattern of itch intensity over time in response to strong, short-term heat stimulation in two different models of histamine and cowhage-induced itch. Moreover, the purpose is to evaluate the effect of mild pre-heating of the skin in human experimental models of histamine, cowhage and serotonin. Finally, we want to investigate the effect of short-term intense heat stimulation on previously anesthetized skin.

Inclusion Criteria:

• Healthy men and women
• Age 18-60 years
• Able to speak and understand English

Exclusion Criteria:

• Suffering from chronic disease
• Pregnancy or lactation
• Prior experience of adverse effects from anaesthetic, specifically Lidocaine
• Drug addiction defined as the use of cannabis, opioids or other drugs - 5 -
• Previous neurologic, musculoskeletal or mental illnesses
• Lack of ability to cooperate
• Current use of medications that may affect the trial
• Active skin diseases
• Active participation in other experiments currently ongoing or within the last 14 days
• Tattoos on volar forearms that will interfere with local skin measurements

Only the third sub-study is conducted in a double-blind manner.