Neurodermatitis is a skin condition that begins with an itch. The itch can develop anywhere on the surface of the body. Most commonly, though, an itchy patch develops on an arm, leg, or the back of the neck. It also commonly develops in the anal and genital areas. When it appears in the genital area, it often appears on the scrotum or vulva. The itch can be so intense that a person scratches or rubs the itchy patch frequently. The itch can also come and go. For most people, the area feels itchiest when they are relaxing or sleeping. The itch causes people to scratch or rub the area while sleeping — and it can awaken someone from a sound sleep.