Fragrance is the sweet, pleasant odor that is sensed by our smeller. It is a word that is closely related to perfume and aroma, but can also be used to describe a specific smell, such as that of pine trees or the scent of flowers. It can also be used to describe a person’s good smell, and the term “fragrance” is often used to distinguish someone from others whose odors are less appealing. The smells of certain foods, such as coffee, are sometimes called fragrances as well. Other words that are related to the concept of fragnance are odor, aroma, and redolence.
Perfume and cologne contain fragrance chemicals in addition to the “scent” ingredients. These are usually derived from natural or synthetic raw materials. Companies that manufacture perfume or cologne purchase their fragrance mixtures from fragrance houses (companies that specialize in developing fragrances) to develop proprietary blends. The resulting mixtures are called formulas. They are then mixed with other ingredients such as diluents and preservatives to make the final product. The diluents are typically alcohol such as ethanol or ethyl alcohol, but may be other neutral-smelling oils such as fractionated coconut oil or liquid waxes such as jojoba oil.
The perfume-oil mixture is the foundation of a fragrance, but can be modified in various ways to create different concentrations: cologne (2% to 5% scent), parfum (15% to 20% scent), and eau de toilette (10% to 15% scent). The perfume-oil concentration determines the amount of scent that will be released when the product is sprayed. The trail of perfume that lingers on the skin after a person is wearing it is known as its sillage. A perfume’s sillage is determined by its ratio of perfume-oil to diluent.
Perfume-oil is extracted from the source material using a variety of processes including steam distillation, dry extraction, solvent extraction, and expression. Steam distillation involves heating the material to high temperatures and condensing it to release the desired aromatic compounds. The process is often repeated with the remaining volatile components. Dry extraction and expression are used for more delicate materials such as fresh fruit rinds and thermally labile oils.
Modern perfumes often use synthetic aroma chemicals to provide odorants that are not readily available or cost-effective from nature. The chemical calone, for example, imparts a fresh ozonous marine scent that is not easy to achieve with natural sources.
Fragrances can be applied to the skin in spray, solid, or liquid form. Most perfumes are formulated to last six to eight hours. The higher the concentration of perfume-oil, the longer the fragrance will last. Fragrances with a lower alcohol content do not irritate the skin as much as those with a higher percentage of alcohol.
The International Fragrance Association and the Research Institute for Fragrance Materials test fragrances to ensure that they are safe to use on human skin. Testing includes hazard identification, dose-response assessment, and exposure assessment. The RIFM’s standards are widely recognized as the best system for achieving safe use of fragrances.