Neat petrolatum

Neat Petrolatum versus Neat SEFA versus Glycerin-Based... 

Petrolatum comprises a complex hydrocarbon mixture that is about 60 to 70% mineral oil, the remainder consisting primarily of paraffin and microcrystalline wax. Despite this composition, the effect of petrolatum on outer SC lipids is distinct from that of mineral oil. As shown in Figure 28.6(a), neat petrolatum forms lamellar-like streamers in the intercellular space, as seen previously.44 The streamers appear to be suspended in a nonstaining or empty intercellular medium,... 

FIGURE 28.6 (a) Neat petrolatum site from a 42-year-old male. Flocculent/fibrous material existing as streamers or bands is present within an otherwise empty-appearing intercellular space, (b) Formulated (10%) petrolatum site. Lamellae, occasionally forming Landmann units, are sometimes separated by a thin layer of more darkly staining amorphous material. Bar = 200 nm. 

The streamer phase observed with neat petrolatum (Figure 28.6[a]) was not observed, but amorphous material was common (data not shown). Reasonable lamellae were occasionally encountered, as shown in Figure 28.6(b). Often these lamellae were separated by thin expanses of amorphous material, as shown in the center of Figure 28.6(b). In general, treatment with formulated petrolatum resulted in an appearance of the intercellular lipids that was much improved over that of neat petrolatum or mineral oil. The corneocytes were more closely apposed, and Landmann units were more common. 

The blinded TEM studies rated the test materials potential to improve lipid ultrastructure as neat SEFA > neat petrolatum > lotion. However, the blinded expert scoring in this study ranked the test materials ability to improve dry skin oppositely lotion > neat petrolatum > neat SEFA. This reversal illustrates two of the roles a moisturizer can play the former showing the materials potential to effect functional improvement and biological repair, the latter showing their potential to cosmetically improve dry skin.47 Importantly, these results demonstrate that the cosmetic and functional aspects of a moisturizer s action on skin do not necessarily contribute to the same extent or need not even act in parallel for a given material or product. 

To conclude this section, previous reports on the beneficial effects of topically applied moisturizing preparations have often focused on optimizing their physiological lipid composition. The results found for the formulated SEFA and petrolatum in this work, when viewed relative to the neat materials, suggest that proper formulation of even nonphysiological moisturizing agents will enhance the beneficial effect these materials have on outer SC lipid structure. 

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