J. Cosmet. Sci., 62, 371–382 ( July/August 2011) 371 Elaboration, characterization, and stability study of a sunscreen emulsion for use as a towelette application in pediatric photoprotection B. CLARES, P. GÁLVEZ, V. GALLARDO, and M.A. RUIZ, Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Granada, Campus of Cartuja, 18071, Granada, Spain. Accepted for publication March 16, 2011. Synopsis The World Health Organization (WHO) estimates that as much as 80% of the solar radiation that an adult receives throughout his/her life is received during the fi rst 18 years (1). Skin protection against harmful solar radiation during this early stage of life is therefore a highly important factor in the prevention of future skin- related diseases. In this respect, recent developments in pediatric dermatology and cosmetic technology have led to remarkable improvements in child skin protection products. However, in spite of these scientifi c break- throughs, many currently available commercial sunscreen formulations have not been well received by the general public, due to inadequate sensory properties, chemical instability, undesirable side effects, and low effectiveness. These disadvantages are not only attributable to the formulations themselves, active principle, and excipients, but also, to a large extent, galenic aspects. The objective of this work was to develop and characterize a sunscreen emulsion for pediatric use, using a towelette as vehicle, to overcome problems of ineffectiveness and formulation instability, and to improve skin-sensory properties. The composition of the towelette, the emulsion, and the presentation format were selected on the basis of the differences between children’s and adult skin. In order to evaluate the chemical stability of the formulation, a study of the organoleptic, physicochemical, microbiological, and rheological characteristics was carried out at 4°, 25°, and 40°C over a period of 30 days. Tests were performed on both the sunscreen emulsion only and the same formulation impregnated within a towel, to test the infl uence the towel may have on the stability of the emulsion. INTRODUCTION Damage from ultraviolet radiation (UV) on human skin is dose-dependent and cumula- tive, and is related to the duration, frequency, and intensity of exposure to solar radiation. Sun causes dermal damage manifested by short- and long-term effects. In the short term, damage may cause burns and allergic reactions related to degranulation and the release of several mediators that play a crucial role in the infl ammatory process, including histamine, Address all correspondence to B. Clares Naveros at beatrizclares@ugr.es.

JOURNAL OF COSMETIC SCIENCE 372 prostaglandins, and cytokines. In the long term, UV radiation may cause erythematogenic and melanogenic harm, as well as immunosuppression and carcinogenesis (2–4), all of which have serious implications for human health. Protection against sun exposure is recommended at all ages, but should be especially encouraged for children and young people, given that a child’s skin is considerably more sensitive to UV radiation than an adult’s. Given that skin possesses a memory effect, exposure to sun radiation during early life leads to cumulative and irreversible damage, which may later be manifested in adulthood (5). Moreover, increasing numbers of children are suffering from sun-related diseases such as photodermatosis (6), and when compared to adult skin, a child’s skin presents histo- logical and physiological differences that make it particularly sensitive to solar radiation (7). In addition, the dramatic increase in the incidence of skin cancer, especially malig- nant melanoma, highlights the need for new and improved prevention methods. In com- parison with an adult’s skin, an infant’s skin is especially delicate, fi ne, and highly permeable. For this reason, a good dermatological sun-protection product must fulfi ll several critical requirements in terms of quality and non-aggressiveness (8). At an early stage of life, skin as a living tissue has not yet fully developed its own natural protection against actinic aggression (9). Exogenous photoprotection is therefore highly recom- mended (10). Given the importance of protection, both educational programs in preven- tion and new formulations for child skin care should be studied (11). Sunscreens are photoprotective cosmetic products that can be designed to cover the der- matological needs of a determined segment of a population with specifi c requirements (12). In addition to the requirements of effectiveness, safety, and versatility (14), the type of sun protection required depends on individual skin characteristics and the purpose for which the product is to be used (13). Characteristics such as softness, waterproofi ng, non-stickiness, ease of application, and a sun protection factor (SPF) of between 15 and 40 are especially desirable in formulations for children. On the other hand, compliance in use in adults is more dependent on the aesthetics of the product. Products with a lower SPF endowed with a lesser degree of waterproofi ng are more generally accepted, because they have less of an unpleasant, doughy, sticky feeling. For this reason, different levels of SPF are incorporated into a broad range of cosmetics for daily use. Skin damage from ultraviolet radiation in early childhood must be avoided through im- provements in photoprotective therapy, and research in this fi eld should aim to produce new sunscreens and/or make already existing ones more effective. The objective of this work was to develop a topical sunscreen formulation for towelette application, as an alter- native to the commercial semi-solid formulations available on the market, and to carry out a stability study of the emulsion used. As a pharmaceutical format, the use of towels as a solid support for sunscreen formulae presents a number of advantages, which include: ease of application, increased stability, a reduction of side effects caused by solar fi lter penetration, and an increase in effi ciency and safety. In addition, the towelette product is more easily conserved due to its single- dose format, does not produce a sticky feeling or generate residues, is easily transported, and is convenient to use. Two tests were carried out to compare the performance of the towelette as a new form of topical application: one on the sunscreen formulation supported within an emulsion, and another on the impregnated towel formulation. Both were characterized for organoleptic