What's the difference between eau de toilette and eau de parfum? Is the price increase worth it?
—Katie A., San Diego

Kick your nose into high gear—it's time for a crash course in Perfume 101. Most perfumes are made up of complex combinations of natural and synthetic materials. Check out the ingredients in Mrs. Obama's luxury scent if you want to see just how specialized a perfume can get. But the truth is, the difference between eau de toilette and eau de parfum comes down to one simple factor.

It's the ratio of alcohol to scented perfume concentrates that determines how the concoction is ultimately labeled. The higher the perfume concentrates, the steeper the price and longer the perfume will last. Here's a rundown of your basic offerings:

• Perfume, or extract perfume, is the most concentrated, with 15 to 40 percent perfume concentrates. Consequently it is the most expensive, and has serious staying power.

• Eau de parfum contains 7 to 15 percent perfume concentrate, is the most popular form of perfume and usually costs less than extract perfume. This type of perfume will definitely linger on your skin.

• Eau de toilette has 1 to 6 percent perfume concentrate, making it the lightest scent and even less expensive. Many women find that this scent just won't stick with them all day.

The actual price increase can vary, but for my signature scent, Marc Jacobs Daisy, 1.7 ounces of eau de toilette costs $57, while the same amount of eau de parfum will set you back $72.

As to whether a higher concentration of those mysterious "perfume concentrates" is worth the 15 or so extra bucks, it's a toss-up. While an eau de toilette will be easier on the wallet, you'll ultimately have to reapply more often, thus using up the bottle faster than if you bought a pricier eau de parfum.

There is, however, a secret to getting the best of both worlds—the staying power of the eau de parfum and the price of the eau de toilette. I'm not talking about simply applying more—that'll just make you smell stronger. You don't want to offend anyone's olfactories, so please, for the love of nostrils, let's sidestep that mistake.

Instead, spray your favorite eau de toilette onto a small sheet of wax paper from a distance of less than an inch. Collect the fragrance droplets with your fingertip and mix a very small amount of petroleum jelly into the perfume with your fingers. Dab the scented mixture where you please, et voilà! You've simultaneously got the long-lasting scent and the lower price tag.

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