This study is a case-control study comparing the skin barrier between 50 T1D patients with healthy controls in 3 age-strata including both pediatric and adult patients.

The skin is a crucial barrier against external allergens and irritants. Therefore the function of the skin barrier is central regarding evolvement of eczema. In patients with type 1 diabetes (T1D) using insulin pumps and/or glucose sensor, eczema is unfortunately a frequent reaction. The skin consists of three layers: epidermis, dermis and subcutaneous fat, whereas epidermis is most determining regarding skin barrier. Epidermis can further be subdivided, where stratum corneum (SC) is the outer part, which means most regarding vulnerability towards external allergens.

The function of the skin barrier can be investigated by non-invasive methods using transepidermal water loss (TEWL), which shows the water vapour flux from the skin. Besides SC can be determined using the tape strip method, where few SC cells are peeled off and thereby can be analyzed with mass-spectrometry. Natural moisturizing factors (NMF) is though one of the very important functionalities of the SC, which are determined by the amount of 2-pyrrolidone-5-carboxylic acid (PCA). Besides, the lipid distribution, presence of antimicrobial peptide and cytokine response give as well important information regarding the skin barrier.

Dermatological manifestations of T1D are quite frequent and have been shown to be related to glycemic control, placing dermatological manifestations as a precursor of other microvascular complications11. There is a lack of studies regarding skin barrier function in patients with T1D, and especially in a pediatric study population. Therefore, this case-control study will be conducted investigating skin barrier function in pediatric patients with T1D compared to healthy controls in order to both meet this lack of knowledge, but as well to improve the prevention of skin problems to devices used in T1D-treatment.

The examination program of just one visit per participant consists of:

• TEWL-measure at forearm and buttock
• Buccal swab regarding filaggrin gene status
• Microbiological swab from the skin at forearm and buttock
• 2X11 tape strips from the skin at foream and buttock to be analyzed for NMF, Lipid, Cytokines, Antimicrobial peptide and Dermal Topographical Index as well as protein content using SquameScan
• Measure of skin PH, hydration and sebum content at forearm and buttock
• Capillary Blood Glucose
• Survey regarding atopic and dermatological symptoms

Cases:

Inclusion Criteria:

• Diagnosed with type 1 diabetes, more than 6 months ago

Exclusion Criteria:

• Skin lesions at both buttocks and forearms so investigation can not be done
• Known skin diseases with decreased barrier function like atopic dermatitis, psoriasis and allergic contact dermatitis
• Active infectious disease
• Use of immunosuppressive medication e.g. steroids
• Lack of language competence in Danish

Controls:

Inclusion Criteria:

• Diagnosed with Tourettes or Headache OR sibling for patients in the 1813-clinic at Pediatric Emergency Toom OR Hospitalized patients at Pediatric department OR Parents to alle these

Exclusion Criteria are equal to exclusion criteria in cases

Study Population are included from the Pediatric department in the diabetes group for patients and primarily in the neurogroup for controls. Adult cases are included from Steno Diabetes Center Copenhagen and adult controls as parents to patients included.