Most of us take for granted that the products we apply to our skin every day are safe and effective. For the vast majority of cosmetics and topical drugs, that is the case. Few products have been used on the skin for as long as mineral oil and petrolatum. Familiar products such as Blistex, ChapStick, Neosporin and Vaseline contain these ubiquitous ingredients. Many of these topically applied OTC drugs and cosmetics have stood the test of time. Yet, mineral oil and petrolatum are regarded by some cosmetic marketers as not natural, unfashionable or even unsafe. It can be argued that these products, derived from Mother Earth, are indeed natural—they are certainly not synthetic. Extensive research has been conducted to measure the safety and effectiveness of hydrocarbons. This article concentrates on the safety and efficacy of the ubiquitous hydrocarbons—mineral oil and petrolatum.
Specifications and Regulations
Mineral oils and petrolatums are composed primarily of saturated hydrocarbons. Most of those hydrocarbons are saturated rings (cyclo-paraffins) or branched chain paraffins (iso-paraffins).
Petrolatum can also be considered a two-phase system composed of microcrystalline wax (solid) and mineral oil (liquid). In some of the studies cited in this article, petrolatum per se was not listed as a test material, but the components, mineral oils and petroleum waxes, were tested and therefore the studies are valid for petrolatum as well.
For decades, consumers have been using cosmetics that contain refined petroleum-based ingredients.
It is imperative to recognize that the degree of refinement of mineral oil and petrolatum is the key to safe and successful cosmetic formulations. Simply using the terms “mineral oil” or “white oil” or “petrolatum” or “petroleum jelly” is not sufficient. If the term mineral oil is not properly defined, it can refer to the oils used in industrial and automotive lubricants. Likewise, unrefined petrolatum can also be used in industrial applications.
Case in point is the CAS number normally used for petrolatum, 8009-03-8, which does not say anything about the degree of refinement of petrolatum. In essence, the same number is used for raw and refined petrolatum. As a result, petrolatum with the CAS number 8009-03-8 was included the EU’s Consolidated List of C/M/R (Carcinogens, Mutagens, or Toxic to Reproduction) Substances.1
However, that petrolatum entry does include the notation; “N” that states: “The classification as a carcinogen need not apply if the full refining history is known and it can be shown that the substance from which it is produced is not a carcinogen.” Clearly, “the full refining history” of USP grade petrolatums exempts them from the list. A detailed explanation of petrolatum CAS issues was described by the author at the November 2003 NPRA (National Petrochemical & Refiners Association) meeting in Houston, TX.2
The specifications for mineral oil and petrolatum were established many years ago by pharmacopeias in the US, Europe and Japan. The US FDA also established purity tests that are published in the Code of Federal Regulations (CFR). Products that pass these tests may be used in both direct and indirect food applications. Similar specifications are found in the Food Chemical Codex.3 For formulators, it is important that they choose ingredients that are certified by the manufacturers to comply with White Petrolatum USP, Petrolatum USP (Yellow), Mineral Oil USP (Heavy) or Light Mineral Oil NF standards.4 For North America, the established manufacturers also certify that these products meet the purity requirements in 21 CFR 172.880 and 21 CFR 172.878 (for petrolatum and mineral oil, respectively). Depending on their physical properties, these products will also comply with similar monographs in the pharmacopeias for Europe and Japan.
Allergenicity, Carcinogenicity & Comedogenicity
Naturally, the first question that arises about topically applied products is the degree to which they are absorbed into or passed through the skin. Elias, Ghadially, et al did extensive research on skin absorption of hydrocarbons.5,6 Those studies showed that typical hydrocarbons found in petrolatum and mineral oil penetrate into the outer layer of the epidermis, the stratum corneum (SC), but very little reaches the lower layers of the epidermis and virtually none of the hydrocarbons reach the dermis. Therefore, any reports that topically applied mineral oil or petrolatum is absorbed through the skin and has a systemic effect are in conflict with the published literature.
In addition to their long history of use on human skin of all ages, mineral oil and petrolatum are among the most extensively tested materials in the world. In the 1980s, mineral oil and petrolatum were shown to have no adverse effects in eye and skin testing on rabbits in studies conducted by an accredited laboratory.7 The fact that mineral oil and petrolatum are so inert is certainly a contributing factor to why they do not typically cause allergic reactions when applied to the skin. They are primarily composed of saturated hydrocarbons, which do not easily oxidize or metabolize. In the absence of proteins, carbohydrates, fatty acids, fragrance chemicals, pesticide residues, etc., it is understandable why these materials do not cause harm to the skin.
Doom-Goossens of the Katholieke Universiteit Leuven monitored the allergic responses to petrolatum containing products during a five-year period.8 Only three cases of allergencity were reported even though the petrolatum was used in more than 500 products. As research on hydrocarbon allergenicity continued, another study was commissioned to measure skin sensitization by petrolatum. This time, Guinea Pig Sensitization tests using petrolatum were reported by Mahagaokar.9 In this study, five male and five females were tested using the EPA Pesticide Assessment Guidelines of 1984 with the Beuler modification.10,11 The study showed that the petrolatum produced no effects at 24 hours and at 48 hours after challenge; again supporting the absence of skin sensitization in case of refined petrolatum.
Polycyclic aromatic hydrocarbons (PAHs) are the only non-saturated hydrocarbons found in mineral oil and petrolatum that are of concern. The levels of PAH are very low in petrolatum and even lower in mineral oil and these low levels are dictated by FDA purity regulations. A sample of White Petrolatum USP was recently tested for specific PAHs by the Biochemisches Institut für Umweltcarcinogene in Germany.12 Out of the 28 individual PAHs analyzed, none exceeded 10 micrograms per kilogram (ppb). This indicates that even though PAHs are present, the concentrations are inconsequential.
Since mineral oil and petrolatum have been used in food applications, it is natural to expect that regulators would request extensive testing for those applications. This was originally done in the 1950s and 1960s before the FDA approved the use of these materials for food contact. Shubik, Lijinsky, et al at The Chicago Medical School undertook a large program of research on 36 samples of petroleum waxes typically found in petrolatum.13 Their work involved lifetime feeding studies of rats with waxes at 10% of the diet. They also conducted repeated skin painting experiments on mice and rabbits. The results showed absolutely no carcinogenic response when compared with control groups.
Another group of researchers at the FDA laboratories and the Sloan Kettering Institute investigated several commercial sources of petrolatum in rat and mice diets.14 This work also resulted in the same conclusion; there was “no toxic or carcinogenic response” after two years in the rat diets, essentially deeming petrolatum safe for direct and in-direct food contact.
More recently, several rat-feeding studies were conducted using various mineral oils and petroleum waxes.15,16,17 It was concluded that a small portion of the hydrocarbons in low and medium viscosity mineral oils, as well as in a low melting point wax, were absorbed in the 90-day feeding period. They accumulated in the livers and mesenteric lymph nodes of Fischer 344 Rats. This resulted in the formation of lipogranulomas in the mesenteric lymph nodes and in the livers. Pathologists described this as a normal inflammatory response to a foreign substance and it was not considered toxic to the animals.18,19 It appeared that the hydrocarbons were so inert that it simply took some time for them to begin to be metabolized. Another protocol involved a two-year feeding study of Fisher rats and the results were similar. All of the studies indicated a greater absorption for lower molecular weight hydrocarbons and a decreased absorbance of higher molecular weight components. An additional Japanese study using a mixture of eight different sources of mineral oils was conducted in 1997.20 They also used Fischer 344 Rats for feeding studies and they found “no statistically significant increase in the incidence of any tumor type.” After numerous animal-feeding studies by several laboratories involving hundreds of rats, there was no evidence of a carcinogenic response to ingestion or topical application of either mineral oil and/or petrolatum.
Researchers have found that cosmetic grade mineral oil and petrolatum are non-comedogenic. It is understandable that people may think that the oily nature of these materials could cause acne. However, Kligman’s 1996 article entitled: “Petrolatum is not Comedogenic in Rabbits or Humans: A critical reappraisal of the rabbit ear assay and the concept of “acne cosmetica,” attempted to set the record straight. He further pointed out that “comedogenicity has nothing whatever to do with oiliness” of the products used.21
Key Moisturization Properties
Healthy and vibrant skin depends on water entrained in the SC. The natural moisturization factor (NMF) in the corneocytes (keratinocytes) of the SC binds water inside of these cells. The surrounding lipid bilayers help retain water. For normal skin under ideal conditions, it may not be necessary for people to use moisturizers. Unfortunately, skin is not always normal and conditions are not always ideal. This leads to the need for good moisturization products. It is well known that mineral oil and petrolatum are effective moisturizing agents because they are occlusive to the skin. In fact, petrolatum is regularly used as positive control for moisturization testing. Dr. Leslie Bauman, MD, states in her 2009 textbook, Cosmetic Dermatology, “Two of the best occlusive ingredients currently available are petrolatum and mineral oil.”22 Chapter 12 of Leyden and Rawlings’s 2002 book entitled Skin Moisturization points out that “petrolatum is considered a standard emollient for comparative testing of hydration and barrier repair.”23 The Ghadially, Sorenesen and Elias paper made use of Evaporimetry to measure enhanced barrier recovery of human skin using petrolatum treatment. The lipids in the SC were partially removed using acetone. This increased the TEWL levels to at least 16g/m2/Hr and the petrolatum treated areas consistently showed faster barrier recovery than the untreated areas. The implication is that petrolatum may function beyond simply as an occlusive agent on the skin and actually provides barrier recovery.
Extensive research has revealed no evidence that mineral oil and petrolatum, which have been refined to meet the most stringent purity specifications, are harmful to the skin in any way. On the contrary, they provide moisturization and barrier repair to damaged skin. Unlike some natural products that can have variable compositions and have not been extensively tested, mineral oil and petrolatum have consistent compositions and have been used on human skin for as long as any modern cosmetic ingredient; in fact, they are still used in many of the most popular brands to date. Their safety has been confirmed by long-term use and by multiple studies indicating that both mineral oil and petrolatum are not comedogens, irritants, allergens and certainly not carcinogens.
About the Author
Harold Faust holds a BS in Chemistry from Duquesne University and has worked with raw materials for the personal care/pharmaceutical industry for more than 38 years. He has held laboratory and technical service positions for global organizations such as Penreco, ConocoPhillips, Pennzoil and Calumet and has published several articles in technical journals on mineral oil and petrolatum. Faust is a member of the Society of Cosmetic Chemists, American Chemical Society and has worked with other organizations, such as the Personal Care Products Council, on projects involving mineral oil and petrolatum.
More info: Harold Faust, email: Hal.firstname.lastname@example.org; Website: www.calumetspecialty.com
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