What sorts of things do people with OCD fear?

Kate is a 33-year-old mother of five from Dallas who is obsessed with cleanliness and terrified of germs. She says she spends up to five hours a day cleaning her already-immaculate house. She arranges items in her house in twos and lines up and trims the fringe on her rugs.

Brian uses his right hand for everything and keeps his left hand in his pocket to protect it from germs. He's terrified of using the bathroom in his house and keeps the bathroom door closed because he doesn't like looking at his toilet. He says he even urinates outside.

Janene is a teacher from Mississippi and mother of twins. She says her OCD takes many forms like hoarding and repeatedly checking locks, switches and knobs. She also says she has major control issues and has trouble letting her kids play outside.

April's OCD fears are about food. Because she won't eat or drink anything she thinks could be contaminated or poisoned, she has lost 30 pounds. "I basically quit eating," she says.

To help these four, along with two other sufferers, Corbin and Kathy, overcome OCD, Dr. Oz arranges for a group session of "OCD Boot Camp" with Dr. Jonathan Grayson at a YMCA camp outside Philadelphia. Dr. Grayson is a leading expert who uses a groundbreaking therapy called "exposure and response prevention." In this therapy—which is recommended by the American Psychiatric Association and the American Psychological Association—patients confront their biggest fears head-on. "They have to confront the possibility of their worst things occurring because there is no other life," he says.