Safe and effective lipids for new mineral oil- and lanolin-FREE formulations

Published on Healthy Chemistry  

Oils, waxes and their derivatives constitute a very large and important class of basic cosmetic and pharmaceutical raw materials. They are used mainly as vehicles and emollients for a very wide range of creams, lotions, ointments, lipidic gels, oils, pastes and soaps. Lanolin, mineral oil, petrolatum and isopropyl esters are the raw materials most often found in topical ointments and emulsions. As it has been largely demonstrated in the past years all these lipidic components present not neglectable drawbacks which suggest their total or partial substitution with safer raw materials having the same effectiveness. Vevy Europe will present the results of research studies regarding the formulation of “alternative” ointments, absorption bases and emulsions containing no mineral oil, petrolatum, lanolin and IPM or IPP, but safe and effective raw materials for dermatological and cosmetic application. Here follows a brief review on the properties but also the inconveniences of the traditional substances found in topical products. Lanolin has been one of the most extensively used ingredients in topical preparations throughout the centuries. Indeed the use of lanolin was known to the ancient Greek since 700 B.C. It is the lipidic secretion of the sebaceous glands of the sheep and chemically it is a complex mixture of esters, diesters and hydroxyesters of high MW, lanolin alcohols and acids. Lanolin is an effective emollient. It softens and improves dry skin by retarding TEWL with a milder occlusive effect compared to petrolatum. However, apart from the pesticides content issue, the incidence of allergy and sensitization to lanolin and its derivatives has been reported in several papers. Nevertheless we should quote Maibach for the best conclusion on the matter “It is folly to state that lanolin allergy doesn't exist; nor it is proper to consider it very common. It is common enough to justify significant work to minimize it”. Petrolatum, also known as petroleum jelly or vaseline, is a purified yellowish to light amber or white complex mixture of semisolid hydrocarbons, chiefly of the methane series having carbon numbers predominantly greater than C25. Actually petrolatum is a colloid system of non straight chain saturated crystalline hydrocarbons and high-boiling liquid hydrocarbons. White mineral oils are viscous liquid derived also from petroleum. They are complex mixtures of saturated hydrocarbons, having carbon numbers in the range of C15 to C50. The chemical and physical properties of white mineral oils are defined by a number of national and international standard setting groups dealing with food, pharmaceutical and cosmetic specifications. Petrolatum and white mineral oils have been used in topical preparations since the beginning of this century. They are excellent moisturizers and emollients and found very quickly markets in cosmetics and pharmaceuticals, e.g. baby oils, sunscreens and suntan oils, emollient creams and lotions, bath oils, lipsticks, make-up, make-up removers, hair care formulations, etc. In pharmaceuticals petrolatum and white oils provide a convenient anhydrous base for topical products, while the higher viscosity white oils are also used as laxatives. In February 1989 the U.K. Ministry of Agriculture, Fisheries and Food recommended a ban on almost all direct food applications of mineral hydrocarbons including white mineral oil. This decision was based, in part on the results of two 90-day toxicity studies in rats conducted using white oils. These studies demonstrated accumulation of oil in the mesenteric lymph nodes and liver, accompanied by microgranuloma formation at the highest dose levels. However other animal studies have not shown such effects and there has been no indication that absorption of white mineral oil has had any adverse effect on humans despite many years of use in pharmaceuticals, food and cosmetics. Later we shall discuss more data on mineral oil and petrolatum safety, remembering Butcher’s studies showing acanthosis and parakeratosis (hypertrophy of the stratum corneum with imperfect maturation and differentiation of keratinocytes) following repeated application of mineral oil. Isopropyl esters are used to produce a light, non-greasy, emollient skin feel. Results presented by Lanzet show that all isopropyl esters, but mainly myristate, linoleate and lanolate, are comedogenic.

Side effects due to traditional lipids

Some drawbacks have already been introduced, while now we’ll survey different researches performed by various investigators. According to Lanzet, only lanolin derivatives which contain the acid fraction (e.g. lanolic acid, isopropyl lanolate, acetylated lanolin alcohol, hydrogenated lanolin) are comedogenic. Recently Fulton surveyed, using the rabbit ear, the comedogenicity and irritancy of several skin care raw materials. Comedogenicity, or ability of test substance to produce follicular hyperkeratosis, and irritancy, or ability of test substance to produce surface epithelial irritation, were evaluated on a scale of 0 to 5, being 5 the worst grade. Several lanolin derivatives are both comedogenic and irritating, sometimes due to other additives. Many esters, and especially isopropyl esters scored high comedogenicity and irritancy numbers. Mineral oil, but also several plant oils, gave a moderate to extensive increase in follicular keratosis. Several examples of side effects due to vehicle constituents are reported by Nater and De Groot. The estimated frequency of sensitization for contact allergy is considered rare for IPM and petrolatum, uncommon for lanolin and sesame oil. Conversely Maibach reported on chronic dermatitis and hyperpigmentation from petrolatum, while lipogranuloma and myospherulosis from petrolatum were discussed by Dunlap et al. Following an assay on the rabbit ear, Kligman et al. suggested that some compound for topical use, including IPM, lanolin, olive oil, peanut oil, cocoa butter and sesame oil, had acneigenic properties. Contact allergy to lanolin contained in face cosmetics is reported by Cronin and by Schorr. Fischer reported on contact allergy to IPM in feminine hygiene cosmetics.

Alternative raw materials

To overcome traditional formulation and the side effects connected to the substances reported above, to improve anhydrous cosmetics appearance, skin feel, stability, etc. we have performed several formulation studies substituting petroleum derivatives, lanolin, isopropyl esters and also vegetable oils with suitable Vevy Europe raw materials. We also replaced natural vegetable oils because they may develop rancidity and malodour due to their content in unsaturated fatty acids. Nesatol (Vevy codex 03.0197) is a reconstituted vegetable-based oil containing saturated fatty acids resistant to oxidation, having good solubilizing properties, imparting a soft feel and having a low skin irritation potential. Moreover some authors found that capric/caprylic triglyceride, peach kernel oil, sweet almond oil, grape seed oil, etc. exhibit comedogenic effects. PME (Vevy codex 03.0775), and also newer PME-1 (Vevy codex 03.3392) are non occlusive substitute for petrolatum; Syntesqual (Vevy codex 03.1133) substitutes mineral oil; Lanolide (Vevy codex 02.0911) replaces lanolin; Isostearene (Vevy codex 03.0373) replaces IPM, Lipocerite (Vevy codex 03.0465) and Cetacene (Vevy codex 03.1350) replace vegetable butters.

Complete article published on Lexicon Vevy Europe 1994, 1:11-13.