Gutter guards don't solely cause ice dams. Ice dams can be caused by many things, like a lack of attic insulation, poor ventilation, or an uneven roof temperature. Gutter guards prevent snow and ice from entering your gutters. As snow from higher on the roof melts, the water can't flow to the gutters, which can refreeze, causing ice dams. If you live in a cold climate, consider investing in heated cables designed to prevent ice buildup on your roof and have good quality gutter guards installed.