What is a petroleum by-product that has excellent sealing properties to hold moisture in the skin?

The correct response is paraffin, which is a petroleum by-product known for its excellent sealing properties. It is commonly used in skincare treatments, particularly in moisturizing applications. When applied to the skin, paraffin creates a barrier that locks in moisture, preventing trans-epidermal water loss. This makes it effective for treating dry skin, as it helps to maintain hydration levels for an extended period.

In contrast, essential oils are derived from plants and are primarily used for their aromatic and therapeutic properties rather than for sealing moisture. Dimethyl urea is often used as a conditioning agent and can improve skin hydration, but it doesn’t have the same sealing properties that are characteristic of paraffin. Methylene glycol, on the other hand, is not typically associated with moisture retention and is more commonly used in other contexts, such as in industrial applications.

The unique capacity of paraffin to form a moisture-retaining barrier is what makes it the preferred choice in this instance.