Body surface area (BSA) is a common way to determine psoriasis severity. Psoriasis involvement of 10% BSA or more is considered "severe”. Traditionally, the impact of psoriasis on quality of life is thought to mirror disease severity. However, according to recent research conducted by the National Psoriasis Foundation (NPF) and the International Psoriasis Council (IPC), psoriasis on certain areas of the body has an outsized impact on quality of life and is associated with depression and decreased participation in social roles and activities, independent of an individual's total BSA. 
Most high-impact sites, also called special areas, are on highly visible areas of the body and have more sensitive skin which can complicate the use of topical therapies. Highly potent topical steroids can cause thinning of the skin and are generally avoided or used sparingly on areas of the body with sensitive skin. Some high-impact sites absorb steroids more quickly (e.g., genitals) or may have particularly thin skin (e.g., area around the eyes) making them more susceptible to the adverse effects of topical steroids.
Treatment for High-Impact Sites
Having psoriasis involving 10% or more BSA is a common requirement to be eligible for systemic therapies. Consequently, people with less than 10% BSA are often treated exclusively with topical therapies, even if they have psoriasis on high-impact sites.
The updated recommendations state that patients who meet one or more of the following criteria should be candidates for systemic therapy :
- 10% or more BSA
- Psoriasis on high-impact sites
- Topical therapy failed to control symptoms
NPF and IPC, along with leading dermatologists, are working towards changing federal recommendations, which are used by many insurance providers to determine which treatments are covered.