Fragrance is a combination of chemicals that give perfumes and colognes their distinct scent. The ingredients can be derived from petroleum or natural raw materials, and are purchased by companies that manufacture fragrance products such as perfumes and colognes. Perfumes may contain several layers of complex scents and are formulated with “head” notes (like citrus fruits or light berries) that evaporate quickly, heart notes that form the body of the perfume and base notes which are long-lasting [1].
Many modern perfumes use synthetic odorants because they can provide scents that cannot easily be obtained from natural raw materials. For example, a perfume containing a floral scent might need to include linalool or coumarin compounds that cannot be produced naturally, but are cheaply synthesized from terpenes or other natural aromatics. In addition to perfume bases, many fragrances also contain various extracts of flowers or other plants that add a distinctive quality to the fragrance.
Some perfumes are made from a blend of pure essential oils, but most are manufactured from synthetic raw materials. The International Fragrance Association and the Research Institute for Fragrance Materials set voluntary standards for the chemicals used in the fragrance component of products, so the cosmetic industry is self-regulating in this area.
Scent plays a big role in how we perceive the world around us. For example, the smell of rotting fruit or sewage was once so repulsive to people that they had to wear masks while walking through cities. But we can overcome aversions to certain smells by becoming used to them. This article from the New York Times explores the surprisingly fascinating science behind the art of perfume making.