Editor’s note: This two-part article was originally written following a discussion among skin delivery experts on the technical aspects of topical formulations used in the cosmetic and pharmaceutical industries, with the aim to identify future trends in delivery. This second installment continues a discussion from Cosmetics & Toiletries magazine’s May 2008 issue and is also based on a chapter written for the book Skin Barrier: Chemistry of Skin Delivery Systems. Practical information for the cosmetic formulator regarding optimization of skin delivery has been added.
The first installment discussed the major developments in skin delivery in terms of formulation, in addition to special delivery considerations for the cosmetic formulator. This second installment discusses: • What are the unsolved technical problems in skin delivery? • What are the latest scientific developments that may influence the direction of skin delivery research? • What areas of research should be focused upon to be ready for the next generation of cosmetic and pharmaceutical product forms?
After the complete discussion, it was generally concluded that although pharmaceutical and cosmetic formulations differ considerably because of regulatory and customer requirements, they share the same deficiencies with respect to skin delivery characteristics.
Unsolved Technical Problems in Skin Delivery
There are a few unsolved technical problems in skin delivery; however, a recent insight in dermatology will need to be discussed first. Skin conditions have changed over the last 30–40 years and more people are suffering from eczema as a result of environmental factors. For example, the incidence of atopic eczema in children rose from 5% in 1950 to more than 25% in 2000 and is still on the rise. This reduced skin barrier function as a consequence of diseases like atopic dermatitis also leads to an increased risk of allergen penetration.
These factors require both industries to look carefully at the excipients included in topical formulations. Unfortunately, many chemicals that help to enhance the penetration of drugs through the skin also increase irritancy3 and these two effects are often linked. Therefore, new formulations being developed should take these environmental factors into account (see Excipients and Delivery).