When left untreated, psoriasis and rosacea can have long-term health and psychosocial implications. The purpose of this study was to estimate the percentage of Americans with psoriasis or rosacea who are not being treated. Patient data from a large claims-based database were analyzed to identify the number of patients who are treated for psoriasis or rosacea. The numbers of patients treated were compared to the estimated prevalences of these diseases in the general population, identified from previously published sources. Of the 18,632,362 patients in the database, 140,439 (0.75%) were seen for psoriasis and 165,130 (0.89%) were seen for rosacea. Based on published sources, 3.2% of Americans have psoriasis and about 5.0% have rosacea. We therefore estimated that 77% of people with psoriasis and 82% of people with rosacea are untreated. Greater awareness, resources, and community outreach projects are potential tools that could eliminate this disparity and increase the quality of life for patients with these diseases.