Step 1: Understanding the Concept:
An emollient is a substance that softens or soothes the skin. It works by filling the gaps between skin cells with droplets of oil, making the surface smoother.
Step 2: Detailed Explanation:
1. Almond Oil (\textit{Prunus amygdalus}): It is a fixed oil rich in fatty acids (oleic and linoleic acid) and Vitamin E. It is non-comedogenic and very effective at moisturizing the skin and improving complexion.
2. Application: It is the most common "base" oil used in high-end cosmetics, massage oils, and baby products for its skin-softening properties.
3. Others: Lavender and Rosemary are volatile oils primarily used for their fragrance (aromatherapy) or antimicrobial properties. Sandalwood is also a volatile oil valued for its fragrance and cooling effect.
Step 3: Final Answer:
Due to its rich fatty acid profile, Almond oil is the preferred herbal choice for emollient cosmetic applications.