Sources Of Information

The Acid Mantle and Natural Skin pH:

Eucerin & Dermatological Research: Healthy human skin is covered by a protective acid mantle. According to clinical dermatological studies, the optimal pH of the skin ranges between 4.7 and 5.75, making it naturally acidic. This barrier of water and lipids is responsible for how external molecules (like those in a perfume) adhere and react.
the International Journal of Cosmetic Science: Cosmetic chemistry studies indicate that alterations in this natural acid mantle (due to harsh soaps, weather, or genetics) change the way topical ingredients, including essential oils, break down and oxidize on the epidermis.

The Effect of Acidity and Alkalinity on Olfactory Notes:
The Chemistry of Fragrance: Olfactory molecules react to the potential of hydrogen (pH). On skin with a highly acidic pH (closer to 4.5), the molecules of base notes (such as vanilla, woods, and gourmands) tend to anchor better and project in a more intense and sweeter way. Conversely, a more alkaline pH rapidly breaks down the volatile esters of top notes (like citrus), significantly shortening their longevity.

Hydration and Molecule Retention:
Cosmetic Chemistry Journals: The hydration of the stratum corneum (the outermost layer of the skin) is fundamental for fragrance fixation. Lipid-rich skin (with good hydration and natural sebum) acts as a physical anchor for perfume oils. Dehydrated skin quickly absorbs available moisture, evaporating the perfume's alcohol and aroma prematurely