The primary function of epithelial tissues is to form a barrier between the body and the external environment, in order to protect the internal tissues from environmental stresses, by minimizing water loss and preventing the entry of pathogens, pollutants and allergens. Allergic disorders, such as atopic dermatitis, have been associated to an impaired epithelial barrier function. Indeed, defects in the epithelial barriers allow tissue-damaging factors to enter the tissue and thus activate the immune response. This study aims to establish a method to assess the epithelial barrier function in vivo by electrical impedance (EI) spectroscopy, a new technique for the characterisation of epithelial tissue. By this technique, a harmless electrical signal is sent through the skin and the response of the tissue is analysed, which is influenced by several cellular properties, such as shape, orientation and size. In order to validate this technique, skin of mice was treated with some molecules able to destroy the epithelial barrier. The investigators observed that, after damaging the barrier, a decrease of the EI can be detected, consistent with the type and degree of the damage.

Based on this result, the investigators believe that this technique is a good candidate as an in vivo method to determine skin barrier defects, which might be used in the future as an early diagnostic tool for the prediction of the risk to develop atopic dermatitis in young subjects, allowing the possibility to apply in time possible preventive measures. In addition, this technique might be suitable for the evaluation of a given therapy during the hospitalisation. To confirm this hypothesis, in the present study patients with atopic dermatitis will be recruited. EI measurements will be performed in both lesional and non-lesional skin and values will be compared in order to detect any difference in the electrical response due to the inflammatory state. In addition, in order to evaluate whether these patients have an appreciable defect in their skin electrical behaviour, the investigators will compare non-lesional and lesional skin of patients with skin of healthy volunteers. Peripheral venous blood and skin biopsies will be collected, in oder to characterise several immune cell populations, to detect specific skin barrier mutations and to measure serum cytokines and immunoglobulins. These and some other parameters and will be analysed in order to identify a possible correlation with the EI.

The inclusion criteria for patients in this study are as follows:

1. Age 0 - 85 years
2. Diagnosis of atopic dermatitis and/or another disease of the atopic group
3. The inclusion of patients in this study is independent from the current therapy. During the study all patients will be kept on a therapy that is medically indicated

The inclusion criteria for healthy controls in this study are as follows:

1. Age 0 - 85 years
2. No diagnosis or history of allergic disease
3. The inclusion of patients in this study is independent from the current therapy. During the study all patients will be kept on a therapy that is medically indicated Written consent will be obtained after detailed information of the study was given to the participant.

Exclusion criteria:

Unable to give consent or refusal to participate in the study

Patients will be recruited from the Hochgebirgsklinik in Davos Wolfgang. Healthy controls will be recruited within the heathy population. All individuals will be sampled for skin, blood and other samples after informal consent.