[header] How to prevent freezer crystals [title] Make sure your freezer is functioning properly. [step] If you are noticing a lot of ice build up in your freezer, it may be a sign that something isn't functioning correctly. One potential problem is is blocked airflow. 
Freezers need to have proper airflow around the cooling coils and vents. If any of the freezer's vents or coils are dirty, blocked or clogged, this could cause an issue with ice build up.