In terms of chemistry, fragrances are a mixture of aromatic oils and alcohol. Perfume has a concentration of oils greater than 22 percent. Eau de parfum has a 15 to 22 percent concentration.
The less aromatic Eau de toilette has 8 to 15 percent oils, and cologne contains less than 5 percent oils. The “fixatives,” or oils that make a fragrance last a long time, traditionally came from animals.
Those have mostly been replaced by synthetic chemicals. The other ingredients came from plants, most notably flowers.