179 Efficacy of Petrolatum mostly straight-chain alkanes of 26 to 30 carbon atoms, while the microcrystalline wax contains isoalkanes and napthene-containing alkanes of 41 to 50 carbons. Petrolatum is a viscoelastic material (both fluid and elastic properties) owing to the presence of partly crystalline lamellar sheets that trap the liquid fraction (7). Paraffin oil can be comprised of hundreds of different species, and its composition and physical properties are largely dependent on processing (6). In fact, the safety and efficacy of petrolatum is highly dependent on the refinement process (8). VPJ is the original branded version of petrolatum, and it is refined to a very high standard that removes unwanted impurities. SAFETY VPJ has been safely used for almost 150 years and is widely used in both cosmetic and pharmaceutical preparations (7). Petrolatum is listed as an active ingredient in the Skin Protectant Monograph for over-the-counter drugs (9) and must meet specification set by the FDA and the European Pharmacopeia (10 and references therein). Petrolatum products that meet purity tests as published in the Code of Federal Regulations are permissible in food products (FDA regulation #21CFD172.880). Thus, petrolatum is safe if ingested only when it is refined to the appropriate standards. PJ is compatible with all skin types, is fragrance-free, is nonirritating (11), is hypoallergenic, and is noncomedogenic (12,13). Despite its occlusive properties and lipidic sensories, PJ can be used to moisturize acne-prone skin without exacerbating this condition (12). Allergic reactions to petrolatum are rare because the saturated hydrocarbons are not easily oxidized or metabolized, and it is frequently used as the vehicle in irritancy, allergenicity, photoallergy, and phototoxicity testing (14). There is no evidence of cumulative irritation potential. VPJ causes no adverse reactions in skin, not only due to its high standard of processing, but also because it remains in the stratum corneum. Numerous studies have shown that the hydrocarbons contained in petrolatum remain almost entirely in the stratum corneum, with few reaching the epidermis or dermis, even when applied on acetone-treated skin (15,16). A review of in vitro and in vivo penetration studies of petroleum derivatives used in cosmetics showed no evidence of systemic exposure from topically application (10). Polycyclic aromatic hydrocarbon levels in petrolatum are very low, as mandated by the FDA regulations cited previously. Numerous studies have failed to demonstrate any toxicity or carcinogenicity of PJ (8). Petrolatum is among the most highly tested materials in the world and has a long history, which confirms the safety of this material both for topical use and by ingestion. UTILITY IN DERMATOLOGY PJ helps promote skin health and healing in persons with compromised skin, including dry, cracked, and chapped skin (hands, heels, lips, angular chilitis, diaper rash) atopic dermatitis (AD) eczema and certain medical conditions. It is endorsed as a post-procedure treatment for minor wound healing and is typically considered the first line of defense against ingress of certain microbes and from external insults. Once considered nonphysiologic, VPJ is not completely inert in fact, compared to other skin treatments, it provides several additional benefits for skin. These include skin barrier recovery acceleration (15,17), preventing infections postoperatively, and stimulating the innate immune response (17).

180 JOURNAL OF COSMETIC SCIENCE XEROSIS Xerosis or dry skin is characterized by perturbed barrier function, increased transepidermal water loss (TEWL), and retention of adherent squames, which leads to the flaky appearance of cosmetically dry skin. Dry skin is best treated by use of a combination of mild cleansers and moisturizers. Moisturizers typically contain a triad of humectants, emollients, and occlusives (13), and petrolatum is one of the most common and effective occlusive agents (18). PJ forms an occlusive layer on the skin, effectively slowing water loss as measured by TEWL by more than 50%, while certain other oils reduce TEWL by less than 20% (19). Water is instead retained in the skin, thus increasing hydration (20) as evidenced by changes in skin capacitance (21). Petrolatum is the gold standard topical agent for reducing TEWL (22,14). As PJ hydrates the skin, skin suppleness and softness is improved. Unlike other occlusive or vapor-permeable products, petrolatum jelly penetrates the stratum corneum where it diffuses into the intercellular lipid domains (15). Penetration of many other oils is limited to the upper layers of the stratum corneum (23,19). A recent study by Choe et al. (24) also observed increased stratum corneum thickness (32% average) with PJ, it but argues that this may be due to changes in increased absorption of water by corneocytes. Importantly, PJ retards water loss without a decrease in the lipid biosynthetic rate (25,15). This potentially increases its efficacy by facilitating the skin’s own barrier recovery. Many actives have been included into moisturizing creams, claiming to provide superior benefits. However, few studies have demonstrated a superior moisturizing effect over VPJ (26). Cosmetic dry skin may result from environmental factors, such as low humidity and cold temperatures, as well as from intrinsic factors such as age. Skin aging is associated with a degradation in skin barrier function, hence senile xerosis and pruritis are common features in the elderly population (27,28). Routine application of an effective moisturizer, such as PJ or petrolatum-based moisturizers, is critically important in maintaining optimal skin condition. Moreover, epidermal dysfunction and a poor barrier have recently been found to contribute to an increase in age-associated systemic inflammation in mice, while daily rehydration lowered levels of circulating cytokines. Maintenance of a healthy skin barrier may extend well beyond the realm of dermal health alone (29,30). AD AND ECZEMA AD is a common inflammatory skin disease that manifests as dry, scaly, erythematous skin. Dysregulation of the innate and adaptive immune responses contributes to the pathophysiology of AD. However, barrier dysfunction is a key feature of the disease (31). Perhaps the strongest evidence to support this later point is the finding that loss-of-function mutations in the filaggrin gene are a major predisposing factor for developing AD (32). Disruption of the skin barrier integrity allows entry of irritants, microbes, and allergens into the compromised skin, and when set in the context of a dysregulated immune setting, this can lead to the development of allergy and asthma—the so-called “atopic march.” The need for routine moisturization is a well-established part of the skin care regimen for AD suffers (33). Maintenance of an adequate barrier may reduce the need for corticosteroids or calcineurin-inhibitors (34). Studies demonstrate that mild to moderate AD can be improved with a PJ-containing emollient cream (35,36). Norman (37) recommends use