Psoriasis is a common, chronic disease that can affect your skin massively. A skin disease that causes red, itchy rough patches, most commonly on the knees, elbows, and scalp. It manages to go in cycles, widening for a few weeks or months, then falling for a while or going for a pause. Eczema is another skin disorder that makes your skin red and inflamed. It causes swelling and an intense itch. you may also see rough, leathery patches that are sometimes extremely dark.