 AD is a chronic inflammatory skin disease characterized by frequent viral skin infections. Recent studies have found that components in the skin of people with AD may block AMP expression. AMPs are responsible for preventing infection from viruses. The purpose of this study is to examine smallpox virus replication and AMP expression in the skin of patients with AD as well as identify other antiviral molecules involved in immune response. These findings will be compared with those of people with psoriasis or asthma, or healthy individuals. This study will consist of one study visit at which skin and blood samples will be taken. 