You don't have to use the essential oils I add to my soap. You're welcome to skip the essential oils, or experiment with other options. If you're using this soap with young children, I recommend skipping the peppermint essential oil, just to be cautious.
The oil and vitamin E are added to moisturize the skin. You're welcome to skip these if you'd like. The oil won't blend with the water, so you'll need to gently shake the soap before use.
Castile soap is a concentrated natural vegetable-based "soap" that greatly differs from the toxic soaps we are accustomed to on store shelves.
When you introduce water into a product without a preservative you always run the risk of introducing bacteria, so use water-based products quickly.