The effects of Iridesse^® on collagen production.

In human skin samples from 10 donors, phosphatidylcholine liposomes improved the penetration of vitamin C (sodium ascorbate), carrying it into the dermis more effectively than into the epidermis, and the liposomal vitamin C reduced UV-induced oxidative and inflammatory markers in the irradiated skin.

Soy-phosphatidylcholine liposomes markedly increased skin hydration and the amount of tretinoin retained in skin in a laboratory model, although intact vesicles were not seen to penetrate (Sinico 2005). In 20 patients, a 0.01% liposomal tretinoin was as effective as conventional gels 2.5 to 5 times stronger over 10 weeks while causing significantly less burning and redness (Schäfer-Korting 1994).

Fluid-state phosphatidylcholines, including soy lecithin, increased the fluidity of model stratum-corneum lipid bilayers and increased the partitioning of test compounds into them, whereas a rigid phospholipid did not.

Reviews of three decades of research conclude that conventional liposomes remain largely in the upper stratum corneum, while specially engineered flexible vesicles (transfersomes, ethosomes) have been shown to carry actives deeper. The field still describes lipid vesicles as a debated class of skin carriers.

In a randomized, double-blind, split-face trial, 33 women applied a 5% alpha-lipoic acid cream to one side of the face and the same cream without it to the other, twice daily for 12 weeks. Laser profilometry showed skin roughness fell 50.8% on the treated side versus 40.7% with placebo; clinical, photographic and self-assessment also favoured the treated side.

Adding 0.5% ferulic acid to a vitamin C (15%) and vitamin E (1%) solution improved its chemical stability and doubled its photoprotection in a pig-skin model (Lin 2005). In a vehicle-controlled human study, the same solution reduced UV-induced sunburn cells, thymine-dimer DNA damage and inflammatory markers after four days of application (Murray 2008).

No published trial has tested retinyl linoleate itself. Skin enzymes hydrolyse retinyl esters to retinol: 44% of the retinyl palmitate absorbed by human skin was converted in one study (Boehnlein 1994). Retinol in turn improved fine wrinkling versus vehicle in a 24-week, double-blind, vehicle-controlled trial of a 0.4% retinol lotion in 36 older adults (Kafi 2007).

In two double-blind, split-face, vehicle-controlled studies of 50 women each, a moisturiser with 5% niacinamide applied for 12 weeks significantly reduced fine lines and wrinkles, hyperpigmented spots, red blotchiness and sallowness compared with the moisturiser alone, and improved elasticity. Separate work showed niacinamide increases the skin’s own ceramide production and reduces water loss in dry skin.

In 76 women aged 30 to 60, 0.1% hyaluronic-acid creams of five molecular weights, applied around the eyes twice daily for 60 days, significantly improved skin hydration and elasticity compared with the vehicle. Wrinkle depth improved only with the lower-molecular-weight grades (50 and 130 kDa), the grades that laboratory imaging shows can pass through the outer skin layer.

In a split-site, double-blind, randomized study of 24 adults with dry, rough skin on the shins, a cream containing ceramides 1, 3 and 6-II applied twice daily increased skin hydration and improved water loss and pH at 24 hours and at every visit through day 28, with benefits persisting seven days after stopping. Earlier work shows ceramides work best alongside cholesterol and fatty acids, the skin’s other barrier lipids.

In 73 women, two weeks of a coenzyme Q10 formula raised Q10 levels at the skin surface and in deeper epidermal layers and, in stressed skin, reduced free radicals and increased antioxidant capacity. The end-points were biochemical, not changes in appearance.

In a double-blind, placebo-controlled study, seven days of topical dexpanthenol improved stratum-corneum hydration and reduced transepidermal water loss compared with the vehicle (Gehring 2000). In a separate study, 1% and 5% panthenol formulations significantly reduced water loss after 30 days of daily use and protected against a detergent challenge (Camargo 2011).

In two investigator-blinded studies of women with moderate-to-severe dry skin (29 and 50 participants), colloidal-oatmeal lotions produced significant improvements in skin dryness, scaling, roughness, moisturisation and barrier measures. Laboratory work in the same papers showed oat extracts reduce inflammatory cytokines and support skin-barrier genes.

In 32 volunteers, a cream containing 25% moringa seed oil applied twice daily for four weeks increased skin hydration by 85% from baseline, against 48% for the identical cream base, with no irritation. The oil’s vitamin E content and antioxidant activity were also characterised.

Thirty women aged 35 to 70 used a serum containing 0.5% salicin, from white-willow bark, twice daily for 12 weeks. Investigator grading showed significant improvements from baseline in wrinkles, tactile roughness, pore size, radiance and overall appearance from week 1, in firmness and mottled pigmentation by week 4, and in instrumental measures of elasticity and hydration at week 12.

In 20 women, formulations containing 0.10% to 0.50% freeze-dried Aloe vera extract applied daily to the forearm for two weeks increased stratum-corneum water content compared with the vehicle alone; transepidermal water loss was unchanged.