No—please, please do not do this. It is a waste of a lot of ingredients.
For starters, vanilla extract is formulated for taste, not scent—and especially not long-lasting scent. It doesn’t tend to smell very nice, and not for long, either.
Secondly, vanilla extract is in an alcohol base, so if added to anything 100% oil based it will bead up, giving you little pockets of brown vanilla extract in your final product.
And for the love of all things sudsy, do not put vanilla extract (or any other cooking extract) in soap instead of essential oils. Readers that have tried this have reported back with disastrous results.
Posted in: Substitutions