Body dysmorphic disorder (BDD) is a mental illness that affects the way you see your body. It’s not about how you look. It’s about how you feel about your appearance. People with BDD are preoccupied with flaws in their appearance that are either imagined or very slight. They often spend hours each day thinking about these flaws, worrying, and trying to fix them. They may also avoid social situations and activities if they think that others will notice their flaws and judge them negatively because of them.