Background: Physical and mental health are cogently enhanced through exercise. Atopic dermatitis (AD) and chronic spontaneous urticaria (CSU) are two common inflammatory skin diseases greatly impacting lives of affected patients. Yet, little is known about physical activity and its implications among patients with these diseases.Objectives: To investigate physical exercise among patients with AD and CSU, exacerbation of the diseases through exercise, and associations with mental health, life quality measures, and disease severity.Methods: We performed a cross-sectional questionnaire study in Denmark on adult AD and CSU patients from two university hospitals and two private dermatology clinics. Included patient-reported outcome measures (PROMs) were Physical Activity Scale 2 (PAS 2), Dermatology Life Quality Index (DLQI), 9-item Patient Health Questionnaire (PHQ-9), 7-item Generalised Anxiety Disorder (GAD-7), Insomnia Severity Index (ISI), Work Productivity and Activity Impairment Questionnaire: General Health (WPAI:GH), Urticaria Control Test (UCT), Urticaria Activity Score over 7 days (UAS7), and Patient-Oriented Eczema Measure (POEM). AD severity was measured with Eczema Area and Severity Index (EASI). Data were non-normally distributed and analysed with non-parametric statistics. REDCap and Stata for Macintosh (Apple Inc., USA) were used for management and analysis of data.Results: In the AD cohort, any amount of exercise was associated with less symptoms of depression (p < 0.001), anxiety (p = 0.043), and insomnia (p < 0.001).Exacerbation of AD through exercise did not affect PROMs. Exercising CSU patients did not differ concerning any PROMs. Concurrent cholinergic urticaria (CholU) was associated with more symptoms of depression (p = 0.006) and anxiety (p = 0.035) and daily activity impairment (p = 0.015).