The present invention provides non-invasive methods for detecting, monitoring, and diagnosing skin disease and pathological skin states such as irritated skin and psoriasis. The methods include using tape stripping to analyze expression in epidermal samples, of one or more skin markers. In illustrative examples, the tape stripping is performed using pliable tape that has a rubber adhesive. Furthermore, the present invention provides methods for predicting and monitoring response to therapy for a skin disease, such as psoriasis or dermatitis. Finally, the methods can include the use of a microarray.