Fragrance (or parfum) is a general term that refers to the complex mixture of chemicals that creates a luxurious and unique scent in a particular product. This ingredient is especially problematic in the U.S., where beauty products are not required to disclose the exact makeup of their fragrance formulas. While many common fragrance components have been known to cause allergies and skin irritation, synthetic musks are particularly concerning due to their potential to disrupt hormones.