Sagging skin contributes to making you appear older and fatigued. This is caused by a decrease in collagen and elastin levels, that normally help keep skin resilient. Exposure to UV rays (specifically UVA rays), combined with aging, can damage cells that produce collagen and elastin. Another factor is drying of the epidermis or top layer of skin. When the epidermis is dry, the dermis layer struggles to maintain its moisture levels, causing more stress on skin. Accumulation of dirt, dead skin and excess fat within the layers of the skin will also cause skin to sag.