* IBD cohort: clinically active disease of the bowel defined either clinically as at least mild activity using dedicated scoring indices (for definitions of disease activity, see below) or biochemically active disease as defined by a faecal calprotectin \> 200 µg/g;
* RA cohort: clinically active disease of at least one joint of the hand as assessed by a rheumatologist;
Age of 18 years or older and mentally competent;
Written informed consent.
IBD patients must already have an ileocolonoscopy scheduled due to a clinical indication.
For female subjects which are of childbearing potential, are premenopausal with intact reproductive organs or are less than 2 years postmenopausal
A negative pregnancy test must be available
Willing to ensure that she uses effective contraception during the study and for 3 months thereafter.
You may not be if
Medical or psychiatric conditions that compromise the patient's ability to give informed consent;
A potential female subject that is pregnant or provides breastfeeding will be excluded from participation in this study.
The exclusion criterium that is specific for RD patients involves a skin type above type 3 according to the Fitzpatrick scale due to feasibility of the MDSFR/SFF spectroscopy measurements.
