Gout is a type of arthritis caused by excess uric acid (a waste product made by the body) in the blood. Everyone has uric acid in his or her body. It comes from substances called purines. Most uric acid comes from purines made naturally by the body. The rest comes from purines in your diet. When the amount of uric acid gets too concentrated, sharp spiked crystals form. These crystals collect in the joints and cause swelling and intense pain. Gout attacks usually come on suddenly, without warning and typically last 12 to 24 hours. The most common area for gout to appear is the base of the big toe, but gout attacks can also affect the ankles, knees, hands, and wrists. If left unattended, gout attacks happen more frequently and can eventually cause permanent disfigurement and damage the joints.