Handmade soap contains glycerin which is a natural byproduct of the soap making process, an excellent moisturizer and also one of the reasons that handmade soap is so good for your skin! Glycerin is an emollient which attracts moisture from the air maintaining moisture in the skin throughout the day.  Store bought, mass-produced bars normally do not contain glycerin and can leave your skin feeling dry and irritated.    Not being real soap, they contain detergents which strip skin of its natural oils.  They use synthetic ingredients to achieve things such as a thick lather or specific hardness of the bar.  On top of being moisturizing, my handmade soap achieves these properties by having the correct ratios of plant-based oils and other natural ingredients.