First, it needs said; there's only 1 real way to remove scent; bind water to the oil and/or fat molecules that the nose picks up as scent (washing), or trick the nose. Overpowering the nose with a "loud" scent is the most common trick, and Febreeze does do this, but that's not all it does. Febreeze's primary active ingredient is Hydroxypropyl Beta Cyclodextrin. Sounds scary, but it's simply a carbohydrate (made during the conversion of corn starch). It's a donut shaped molecule that water can bind to only on the outside, but oil and fat can bind to only on the inside. Basically, the stink gets trapped in the donut. The stink molecules aren't removed, but it doesn't get to the nose receptors because it's trapped in the HP 3B2CD molecule. The biological cause/s of allergies remain a mystery, but if it's related to the size of molecules, then it would be entirely plausible that a person could be allergic to Febreeze, while not (knowingly*) being allergic to fragrances. Natural smells (including dislikable ones) are usually small molecules, but artificial ones are larger. Think about it; the Beta Cyclodextrin is large enough to envelope the small molecules, making them larger that even the molecules of perfumes. So-called "fabric softener" are also pervasively large molecules, larger than artificial scents, because of how they emulate "softening". The order of allergic-ness, based on molecule size would be; 1) Febreeze 2) Fabric Softener 3) Perfumes/Cologne In other words, you can be allergic to 1 & 2, but not 3 - but if you're allergic to 3, you'll be allergic to 1 & 2.
*Not all allergies manifest themselves in ways that are obvious to the victim. I wonder how many people who experience everything from migraines to Tourette's might, actually, just have a scent allergy.
Additional note; packages sent via the US Postal Service are believed to all be tested for explosives. The most common method of passive explosives testing is to blow a testing agent through the package, where the molecules of volatile chemicals can be detected by sensors. It's plausible that this is also done with a Cyclodextrin. Mailed packages all seems to have a Febreeze odor to them. Persons allergic to Febreeze should wear a mask while opening mailed packages, and allow them to air out in an unattended location.View Thread