I love love love water soluble oils! Water soluble oils are oils that have been esterified to become more water soluble. Some of them can be used as emulsifiers - like Cromollient SCE - but all of them can be used in water only creations, like body washes or shampoos.
One of my favourites is water soluble olive oil (INCI: PEG-7 olivate), also known as olive oil esters.
PEG-7 olivate is an odourless and clear to pale yellow ingredient with a pH of 5 to 7, an HLB of 11, and a shelf life of three years. It's soluble in water and alcohol and dispersible in oils. It can be used as a light solubilizer for other ingredients like essential or fragrance oils, and it plays well with gels! Although it's a light feeling ester, it isn't a non-greasy one like cetearyl ethylhexanoate or IPP, and won't reduce the feeling of greasiness in your products. (If you use PEG-7 olivate instead of olive oil in your creations, it will feel lighter and less greasy than the same product with olive oil, but it doesn't feel less greasy on its own.)
I am a huge fan of this ester because you can use it in just about everything! It's used as an emollient, lubricant, anti-irritant, solubilizer, and thickener. It won't reduce foaming in your lathery surfactant products, and it will offer slightly creamier feeling suds, emolliency, and "oil free" moisturizing. It also acts as a thickener, although the thickening I've experienced has been very minor and I wouldn't consider it a true thickener like Crothix or glycol distearate. In my experience, it will thicken water based products, like toners or make-up removers slightly. And as an anti-irritant, it will increase the mildness of your foamy surfactants to make for a more gentle facial or body cleanser.
PEG-7 olivate is a fantastic inclusion in hair care products - shampoo, conditioner, leave in conditioner, styling gels - as an "oil free" moisturizer. You can use it in your cleansers as an additional cleansing ingred...