The science
The formulation difference between Riche and the classic Huile Prodigieuse is a textbook illustration of how emollient choice governs skin feel and persistence. Caprylic/capric triglyceride is a medium-chain coconut-derived triglyceride with a moderate spreading value and good oxidative stability, widely used as a substantive emollient. Decyl oleate is a long-chain ester that absorbs slowly and leaves a lubricating film; it is also flagged in some comedogenicity screens, which is relevant to facial use. Oleic/linoleic/linolenic polyglycerides are polyglycerol esters of the three principal unsaturated fatty acids in plant oils, functioning as occlusive-leaning emollients that reduce transepidermal water loss by forming a semi-permanent lipid layer at the surface. Together they replace the fast-evaporating coco-caprylate/caprate and dicaprylyl ether of the original, which is why Riche measures and feels more persistent on dry skin; the effect is a slower-absorbing, more occlusive film rather than any change in the botanical actives.
The botanical oils contribute fatty acids with well-characterised roles. Macadamia oil is rich in palmitoleic acid, a monounsaturated fatty acid that is a significant constituent of human sebum and declines with age, making it a rational choice for lipid-depleted dry skin. Sweet almond and hazelnut oils are oleic-acid dominant; oleic acid is an effective emollient on intact skin but is documented in the dermatology literature as a penetration enhancer that can disrupt barrier organisation on compromised or atopic skin, which is the basis for the standard advice to avoid oleic-heavy oils in eczema. Borage seed oil supplies gamma-linolenic acid, an omega-6 fatty acid with anti-inflammatory metabolites that has been studied topically and orally for atopic dermatitis with inconsistent results; at its position after the fragrance the dose is low. Argan oil adds tocopherols and linoleic acid, and small studies have reported improvements in skin hydration and elasticity with its regular use. The tocopherol, ascorbic acid, rosemary and tomato extracts constitute an antioxidant system whose primary function is protecting the unsaturated oils from oxidation.
The tolerance profile is dominated by the fragrance. Parfum sits eighth, and the listed components include linalool, limonene, citronellol, geraniol and isoeugenyl acetate, all among the allergens that EU cosmetic regulation requires to be declared, along with bitter orange peel and geranium essential oils. Fragrance is the most common cause of cosmetic allergic contact dermatitis in patch-test populations, and a leave-on oil applied over large areas nightly represents sustained exposure. Nuxe's efficacy claims rest on a 29-volunteer usage test reporting perceived softness and nourishment after 28 days; no independent clinical data on the product exist, and the anti-pollution and stretch-mark claims describe antioxidant content and temporary surface emollience respectively rather than measured protective or structural effects.