For one thing, when manufacturers tell you not to do something with a product, it pays to listen. Check the warning disclaimers on the labels of most popular moisturizers, and you'll see the same advice again and again: "Not for use on broken skin."
There's a reason for this. Back in the day, people mostly relied upon simple mixtures of lanolin and petroleum jelly to soothe dry patches of skin. So they might have been able to get away with putting the same thing on a cut. (Petroleum jelly actually is pretty good for cuts once they've begun to heal -- more on that later.) But in the modern, intensely competitive world of "dermaceutical" and "neutraceutical" skin care products, manufacturers have been compelled to add an increasingly vast array of ingredients -- vitamins, antioxidants, minerals, exfoliating enzymes and the like -- so that they can woo customers with extravagant claims. Some products contain more than three dozen active ingredients [source: Loden].
Maybe some of that stuff will make you beautiful. But when you rub those substances into the fragile environment of an open wound, the results can be pretty awful. Some of the acids in today's miracle multi-function moisturizers are meant to strip away dead debris, for example, so they may irritate vulnerable new skin. Others just don't help cuts to heal. If you're a natural-beauty buff, for example, you might assume that a moisturizer containing a big dose of vitamin E would help regenerate the skin around a cut. To the contrary, in a study published in the journal Dermatological Surgery in 1999, researchers found that vitamin E does nothing to improve the healing of wounds or reduce scarring. Worse, it can cause irritation that may make a scar even uglier [source: Edell].