Around the holidays, potted poinsettias are very popular. The bright red or white leaves add holiday cheer to the home and are often a part of the decorating process for Christmas. As with many Christmas decorations, however, poinsettias can be dangerous to your pets. While not deadly, ingestion of the leaves can cause vomiting and severe irritation to the mouth. A cat or dog with an upset stomach is not what you want to deal with over the holidays, so keep these plants up high or just avoid them altogether.