If you study ingredient labels at all - in household items and even in food, you'll see propylene glycol. 

Propylene glycol (PG) is a colorless, nearly odorless, syrupy liquid that is derived from natural gas. It is used in dozens of products that you commonly use around your house. Some websites and natural product promoters argue that PG is a nasty, carcinogenic chemical that has been wrongly greenlighted by the FDA.

The FDA, and others, say that their claims are completely unfounded - that PG is completely safe when used properly.

Propylene Glycol is used:

• In food – Cake mixes, salad dressings, soft drinks, popcorn, food colorings, fat-free ice cream and sour cream. It also protects food from freezing and helps as a preservative.
• In toiletries and cosmetics – Lotions, creams, some baby wipes (though not in the brand I have in my cabinet), shampoos, antiperspirants, cosmetics, lipstick, lubricants
• In other household items – Room deodorizers, cleaners, sanitizers and yes, new "non-toxic" and "safe" automotive antifreezes
• And specific to the soap making and toiletry making industry, it is also used as a carrier in fragrance oils and in many melt and pour soap bases.

Over the past few years, there has been a lot of controversy about propylene glycol. Many people immediately associate it with diethylene glycol (DEG), a common (and admittedly dangerous) ingredient in automotive antifreeze, and assign guilt by association.

Others refer to MSDS tests where PG was tested in 100% concentrations. Even sand and salt have ominous sounding MSDS cautions at 100%. But in most products, especially in “leave on” applications like lotions and cosmetics, PG is only used in tiny percentages.
You Have to Be an Educated Crafter

It is up to each manufacturer of personal care products, and consumer of the same, to make up their own mind. If you are using a fragrance oil, melt and pour soap base, or pre-made liquid soap or shower gel, chances are, there is propylene glycol in it. You need to understand the ingredients in your products and make an educated choice.

Here are some informative articles about propylene glycol:
From Tom’s of Maine, manufacturers of natural toothpastes and toiletry items
From “The Cosmetics Cop”
More PG safety information
Government Facts
PG and Pet Safety
Wikipedia on Propylene Glycol

And just to be non-partisan, here are some anti-propylene glycol articles:
Baby Wipes Danger
Propylene Glycol - from the Skin Deep Cosmetics Database

So...like I said. Chances are you've been using products containing propylene glycol for years. But that doesn't necessarily make them safe. On one hand, I believe that propylene glycol is fine. On the other hand, I fully support more natural products and the overall reduction of chemicals in our households and bodies.