They are both preservatives.
Propylparaben:
Food grade preservative from nature-identical compounds
Methylparaben:
A nature-identical compound. Useful preservative,
produced from vegetable based oils.
Excellent stabiliser.
This is a preservative, stabilizers are used to keep conditioner or lotion from seperating. Seperation occurs when the oils and water seperate, it looks nasty when this happens.
As nice as it would be to find conditioners or lotions without preservatives it isn't going to happen. Oils and water mixed is just a feasting ground for mold and fungi so preservatives must be used. Even people who make their own add preservatives, unless they keep it in the fridge and only for a short time.
Preservatives are less necessary in soaps or shampoos but that would depend on what was in them.
The most natural preservatives you are going to find is in Burts Bees products. They use a complicated process involving sugars that I couldn't possibly hope to describe as I am lacking a chemistry degree. I have seen others describe it and it made my eyes go
. **BUT** Burts Bees also has a habit of not listing all the ingrediants in their products which has gotten them into trouble with the FDA.
More information on SLS.
http://www.snopes.com/toxins/shampoo.htm you might also check the links to the American Cancer Society at the bottom of the page.
I found a book called "Soapmaking; Making Transparent and Natural Liquid Soap" by Catherine Failor. I am hoping to try the shampoo and bath gell recipes soon.
The transparents recipes are not so natural but the liquid soap recipes sounds lovely.
My hair is pretty crappy too so I am trying this weird thing...
I squeeze out some conditioner then add some Jojoba oil and some glycerine to it then mix and use on my hair.
