Psoriasis is a common skin condition that changes the life cycle of skin cells. Psoriasis causes cells to build up rapidly on the surface of the skin. The extra skin cells form thick, silvery scales and itchy, dry, red patches that are sometimes painful.  Dermatitis, also known as eczema, is a group of diseases that result in inflammation of the skin. These diseases are characterized by itchiness, red skin, and a rash.  Acne is a skin disease that occurs when hair follicles are clogged with dead skin cells and oil from the skin.