Methods of Early Detection and Grading Of Diabetic Peripheral Neuropathy (MEDON)

Inclusion Criteria: 1. Men and women minimum 18 years of age and maximum 75 years of age 2. Signed informed consent form 3. Diagnosed with diabetes type I (for group 1-3) 4. Diagnosed with DPN defined as a threshold above 25-volt biothesiometry or absent feeling on the big toe using 10g-monofilament. (for group 1-2) 5. Answered questionnaire: PainDETECT 6. Nothing abnormal on initial tests (group 4) 7. Accepted initial screening blood samples 8. MRI-compatible participant Exclusion Criteria: * 1\. Current or previous alcohol- or drug abuse 2. Abnormal screening blood samples 3. Not being able to understand Danish written and/or verbally 4. Not being able to corporate to examination (e.g. not being able to speak, suffering from senile dementia etc.) 5. Previous chemotherapy or intake of experimental medicine 6. Active HSV- or VZV-infection or known HIV 7. Known severe skin disease 8. Known neural damage or disease in the neural system (e.g. MS, Guillain-Barre etc.) 9. Critical limb ischemia defined as in current clinical consensus 10. Allergy or intolerance to histamine or inability to make do without for one day 11. Pregnancy 12. Active cancer-disease