Australian tea tree oil (TTO) has a reduced permeation capacity in topical formulations, but its effectiveness in cosmetics and pharmaceuticals remains unaffected.

In vitro studies on release and human skin permeation of Australian tea tree oil (TTO) from topical formulations.

Mineral oils and waxes used in cosmetic products do not present a risk to consumer health due to their limited dermal penetration and absence of systemic uptake.

Review of data on the dermal penetration of mineral oils and waxes used in cosmetic applications.

Nanostructured herbal formulations, such as Carrot Extract and Marigold Extract, can enhance skin hydration and elasticity without causing side effects.

Synergism of plant extract and vegetable oils-based lipid nanocarriers: Emerging trends in development of advanced cosmetic prototype products.

Parabens in cosmetic formulations are absorbed through human skin, with higher fluxes from oil/water emulsions and decreasing lipophilicity as lipophilicity increases, and fluxes becoming constant after about three months of storage.

Percutaneous absorption of parabens from cosmetic formulations

The neutral oil-incorporated liposomal nanocarrier effectively improves skin absorption of ascorbic acid, with camellia oil providing the highest flux.

Neutral Oil-Incorporated Liposomal Nanocarrier for Increased Skin Delivery of Ascorbic Acid

Natural cold pressed oils from seeds and fruit stones can be applied to the skin as cosmetics, with safflower oil showing the best appearance, coconut oil having the best smell, and black currant seed oil showing the best absorbency.

Natural cold pressed oils as cosmetic products

The 24-hour receptor fluid value accurately estimates 24-hour in vivo systemic absorption of retinol from cosmetic formulations, with in vitro skin studies useful for determining whether to include absorbable material in in vitro studies.

In vitro and in vivo percutaneous absorption of retinol from cosmetic formulations: significance of the skin reservoir and prediction of systemic absorption.

Cosmetics may be a significant source of mineral oil contamination in women, with age, BMI, country of residence, previous childbirths, sun cream use, and daily use of hand creams and lipsticks being significant determinants.

Evidence for cosmetics as a source of mineral oil contamination in women.

Lipophilic cosmetic ingredients like dibutyl phthalate, farnesol, and geraniol form reservoirs in skin, and may diffuse out into receptor fluid within 72 hours after application.

In vivo and in vitro skin absorption of lipophilic compounds, dibutyl phthalate, farnesol and geraniol in the hairless guinea pig.

Essential oil components exhibit higher skin permeation when applied in rose oil, suggesting co-operative interactions between components may promote skin absorption.

Comparative study on the in vitro human skin permeation of monoterpenes and phenylpropanoids applied in rose oil and in form of neat single compounds.

This study developed and validated a practical skin absorption model for fragrance materials, using 10%, 40%, and 80% default values based on maximum flux, to estimate systemic exposure when experimental data is lacking.

An in silico skin absorption model for fragrance materials.

In vitro tests using excised animal or human skin are a cost-effective and ethical alternative to in vivo experiments for assessing dermal absorption and percutaneous penetration of cosmetic ingredients.

Test guidelines for in vitro assessment of dermal absorption and percutaneous penetration of cosmetic ingredients. European Cosmetic, Toiletry and Perfumery Association.

Hydrogel lenses resist cosmetic cleansing oil, while silicone hydrogel contact lenses (SHCLs) have different degrees of resistance depending on the lens material, with some SHCLs absorbing more oil under dry conditions than under wet conditions.

Cosmetic Cleansing Oil Absorption by Soft Contact Lenses in Dry and Wet Conditions

The 3D skin model EpiDermTM may be a more suitable alternative for dermatotoxicological studies than keratinocyte-based cell culture, as it better reflects human skin metabolism and xenobiotic metabolism capacities.

Xenobiotic metabolism capacities of human skin in comparison with a 3D epidermis model and keratinocyte‐based cell culture as in vitro alternatives for chemical testing: activating enzymes (Phase I)

Fed-batch fermentation of hydrolysed horse oil produces high-quality and high-yield sophorolipids with potential as cosmetic ingredients for improving human skin quality.

A novel microbial technique for producing high‐quality sophorolipids from horse oil suitable for cosmetic applications

The SENS-IS assay effectively detects mixture effects in skin sensitization studies, revealing potential sensitizing hazards in cosmetic products.

In vitro measurement of skin sensitization hazard of mixtures and finished products: Results obtained with the SENS-IS assays.

Dermabraded mouse skin shows increased cadmium accumulation in lymph nodes and liver, suggesting transdermal absorption of nanoscale materials depends on skin barrier quality.

Quantitative determination of skin penetration of PEG-coated CdSe quantum dots in dermabraded but not intact SKH-1 hairless mouse skin.

Bromochlorophene (BCP) has a 12.20  2.63% dermal bioavailability in gel and cream formulations, with a representative dermal absorption of 12.20  2.63% based on in vivo pharmacokinetic studies.

Pharmacokinetics and the Dermal Absorption of Bromochlorophene, a Cosmetic Preservative Ingredient, in Rats

Niacinamide has a 60-fold lower skin absorption rate than methyl nicotinate, with higher lipid solubility and lower crystallinity of MN.

In Vitro Human Skin Absorption of Solvent-Deposited Solids: Niacinamide and Methyl Nicotinate.

Alpha hydroxy acids (AHAs) show greater absorption at pH 3.0, with similar absorption rates for glycolic and lactic acids, and their ability to penetrate various skin layers and form depots remains unaffected.

In vitro percutaneous absorption of alpha hydroxy acids in human skin

What is the evidence of cosmetic oil and skin Absorption?

These studies suggest that while Australian tea tree oil has reduced skin permeation, mineral oils and waxes have limited dermal penetration, and nanostructured herbal formulations can enhance skin hydration and elasticity.