Wired.com's Patrick Di Justo gives us the breakdown of 11 different chemicals commonly found in shaving cream, and the functions they each serve. I've reprinted the full text below. To see what's in your shaving cream and how it stacks up to others out there vist EWG's Skin Deep Cosmetic Safety Database. Womens's shaving creams compared here.
Thick, rich, velvety – and chock-full of ingenious chemicals, by Patrick Di Justo
• Palmitic acid: This long-chain lipid is found in palm oil and animal fats. A major component in soapmaking, it helps create a thick, stable lather that enfolds follicles and holds them upright.
• Triethanolamine: A thickener and wetting agent, TEA allows water to flow more freely by reducing the surface tension that holds droplets together. It's also a precursor chemical for the blistering weapon nitrogen mustard gas.
• Sunflower oil monoglycerides: This plant oil has seemingly magical properties. Its fatty acids attach to a carbon backbone and keep the product in gel form. But rubbing the gel in your hands introduces air. Voilà: foam.
• Stearic acid: Commonly used in cosmetics, this waxy lipid softens the skin. Combined with TEA, it becomes a powerful thickener for luxurious lather.
• Isopentane: In shaving cream, this degreaser breaks down sebum, the oil your skin produces. (It also smells like gasoline.) That helps whiskers stand up, the better to mow them down with a razor.
• Sorbitol: In food, this sweetener causes diarrhea. (Luckily, shaving cream is not for eating.) Here it's a cheap stand-in for glycerine, a skin moisturizer.
• Aloe barbadensis: You know it as aloe vera – the gooey stuff inside the plant. It's yet another skin softener and probably helps accelerate the healing of nicks.
• PVP: Polyvinyl pyrrolidone sticks to the keratin in hair shafts and, like isopentane, makes the hairs stand up straight for a clean shave.
• Isobutane: A compressible aerosol propellant, it helps the gel squirt out of the can. Pyromaniacs take note: It's also extremely flammable.
• PEG 90M: Polyethylene glycol is a versatile polymer used in laxatives, sexual lubricants, and lots of medications as a binding agent. In nanotech, it serves as a lattice on which biological cells can grow. In shaving cream, it's a lubricant and stabilizer.
• Blue #1: So that's what gives the gel its electric blue tint! When the ingredients are worked into a lather, tiny bubbles indiscriminately scatter all wavelengths of light and the blue disappears.