Dull skin is a term used to describe skin that appears lackluster, dry, and lacking vibrancy. The skin may look dry, flaky, sallow, or even patchy in some areas. Dull skin can be caused by a variety of factors, such as sun damage, environmental pollutants, dehydration, poor diet, stress, and inadequate skincare. If your skin appears dull, it's important to address these causes in order to help restore the skin’s natural luster and glow.