D Limonene is a cleaning agent that is one of the most widely used citrus-based fragrance ingredients. It can be found naturally through extracting oil from citrus peels, and is also produced synthetically. It can be used in place of harsher cleaning agents such as acetone, toluene or glycol ethers. The U.S. EPA has said that D Limonene is safe for use in consumer products. In the European Union, it is one of 26 ingredients that have been designated as a potential allergen for skin. However since we use it at very small concentrations -- in fact, below the level required to be reported in the European Union -- and since our products are not designed to be left on the skin, we feel it is acceptable for use.