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J. Soc. Cosmet. Chem. 29 641-649 (1978) Design and evaluation of a water-resistant sunscreen preparation RICHARD S. BERGER, JAMES A. MEZICK* and CHRISTOPHER M. PAPA Division of Dermatology, Rutgers Medical School, Piscataway, New Jersey and *Dermatological Division, Johnson & Johnson, New Brunswick, U.S.A. Presented at the joint Symposium with the Pharmaceutical Society of Great Britain, 'Cosmetic and Pharmacological Aspects of Colour', 11 November 1976 at Stratford upon Avon Synopsis A water resistant sunscreen preparation was formulated to function during swimming, exercising and sunbathing. The sunscreen agent, oetyl p-N,N-dimethylamino benzoate (PABA) and an ammonium aerylate/aerylate ester polymer were combined in a cosmetically pleasing oil-in-water, fugitive amine, lotion vehicle. When applied to skin, a substantive film forms which does not interfere with transepi- dermal water loss or normal sweat gland function. Double blind clinical studies showed that this water- resistant sunscreen preparation provided protection from sunburn after 60 min swimming in fresh or salt water. This water-resistant sunscreen preparation was found to be safe and of low irritancy, allergenic, sting and stain potential. INTRODUCTION Ultraviolet light (uvl) produces profound effects on human skin. This is especially true for the electromagnetic spectrum in the uv-B region of 290-320 nm. This radiation produces excitation of electrons which leads to chemical changes in DNA of epidermal cells and to the release of vasoactive substances, such as prostaglandins producing painful sunburn and cell destruction (1). This action spectrum is most likely responsible for the in- duction of skin cancers and ageing processes seen with prolonged solar exposure. With increased awareness of these sequelae and the popularity of out-door recreation, there is now a demand for effective products to protect individuals from these effects. In addition, there are a small number of individuals who require products to prevent sun-related exacerbation of underlying diseases, such as lupus erythematosus. Most available sunscreen preparations are removed by active swimming because of the incorporation of a water soluble sunscreen agent or a water-washable emulsifying system-. Our primary objective was to develop a sunscreen preparation for the mass market that would resist removal and provide effective uv-B protection during conditions of normal usage, such as swimming and exercising. Even if individuals are diligent about applying a sunscreen repeatedly, they may get burned while swimming, since water filters out very little uv-B. Therefore, the important feature of water-resistance is needed to protect people during and following swimming. 0037-9832/78/1000-0641 $02.00 ¸ 1978 Society of Cosmetic Chemists of Great Britain 641