Denatured Alcohol
Grain alcohol is a great solvent for scented oils, and it lacks a strong odor. But since some people will drink any alcohol they can find, the Alcohol and Tobacco Tax and Trade Bureau authorizes perfumeries to use denaturants like quassin or brucine to make their potions taste like liquid death. The manufacturers' incentive? It lets them skirt the high taxes on beverage alcohol.
Benzyl Benzoate
Cologne is supposed to evaporate from the skin and seep into noses like the aroma of pie in a Chuck Jones cartoon. Benzyl benzoate prolongs that evaporation without adding any smell. Bonus: It's also a powerful antiparasitic that's used to kill lice and scabies. Just saying.
Diethylamino Hydroxybenzoyl Hexyl Benzoate
DHHB is used in cosmetics throughout Europe as a way to absorb wrinkle-forming ultraviolet-A radiation (light in the 320- to 400-nm range). It's not approved for that in the US, but it can be used to ensure the UV rays don't break down your cologne.
Citral
Citral belongs to a family of chemicals called terpenes, produced by plants to ward off pests and other creatures. It's a mixture of geranial and neral, which together give lemongrass its smell and taste.
Linalool
Another terpene and a common commercial fragrance that combines a floral bouquet with a hint of herbal woodiness. It also inhibits cockroach eggs from hatching and, according to a Japanese study, has a calming effect on restrained rats.
Hydroxyisohexyl 3-cyclohexene Carboxaldehyde
This tongue twister, known as Lyral in the cosmetics trade, is an allergen that causes contact dermatitis in some people. So why include it? Because Lyral is one of the few chemicals that emulate the delicate scent of lilies of the valley.
Limonene
Oil from citrus rinds. The active ingredient in the latest generation of "orange" degreasers, it also has been tested as a biofuel. Here it just boosts Boss' citrus quotient.
Eugenol
Oil of cloves. One of the easiest scents to identify, eugenol has long been held to be an aphrodisiac. It works for mice: A study in India showed that it makes them as priapic as a dose of Viagra would. Hey ladies!
