Introduction: A number of treatments for atopic dermatitis (AD) are available; however, long-term treatment patterns and healthcare consumption in patients with AD are poorly described. Methods: We conducted a registry-based longitudinal drug utilization study among Danish patients with AD that were referred to their first-ever visit at hospital-based dermatology clinics. Their first visit was in the period between 1 January 2005 and 31 December 2012, and patients were followed up to 5 years after their first visit. Results: In total, 8213 people with a first-time hospital dermatologist contact for AD were included in the study (3514 aged 0–9 years, 1501 aged 10–19 years, 3198 aged 20 years or older). At first visit, a baseline history of moderately potent topical corticosteroid (TCS) use was seen among 46.6% of children (0–9 years), whereas potent or very potent TCS use was more frequently among older individuals (e.g., 51.1% and 25.6% of people aged 50 years or older had used potent and very potent TCS, respectively). The median (interquartile range) annual number of visits to general practitioners was 4 (2–7) for children and 5 (2–8) for adults, in the 12 months prior to referral. Three years after referral, these numbers had decreased to 2 (1–4) and 3 (1–6), respectively. In the first year after referral, 6% of patients were prescribed systemic corticosteroids, whereas other systemic therapies were used in 5% or less. Conclusions: After referral, low proportions of patients received systemic treatment, or potent TCS. These findings highlight considerable differences in treatment patterns between general practitioners and private practice dermatologists, compared with hospital-based dermatologists, and emphasize the need for better adherence to evidence-based treatment guidelines.