Zirconia crowns are biocompatible. They do not cause allergies in patients. If you have allergies to porcelain-fused-to-metal crowns, you may switch to zirconia. But you should not take anything for granted. Ask your doctor to do a patch skin test at your consultation meeting. Understanding if you are allergic to zirconia may take hours or even days. You can also ask to see any literature on the clinical trial of zirconia on this topic.