Nothing directly gross. I had a really nice square tin of Peterson holiday aromatic, an elegant blend in a beautifully decorated tin, with fabulous room note -- cinnamon, vanilla, ginger, and pine, or some really holiday array of flavors. But boy that stuff burnt like blazes. Whoo-eee. Then I'd go to brush my teeth with peppermint toothpaste, and I'd climb the bathroom mirror. That started my turn toward the glories of non-aromatic blends. Please.