274 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS These patients with apparent and invisible skin disease formed the basis for a specialty panel useful in evaluating the effect of topical products on sensitive skin. The test product was applied in a concentration and form appropriate for open-patch testing to a 2-cm diameter area between the lateral eye and temple twice daily for two weeks. RESULTS This methodology can be used as a final test to determine the value of products designed for "sensitive skin" once obvious sources of allergic contact dermatitis, comedogenicity, acnegenicity, and contact urticaria have been eliminated. This patient selection meth- odology has more clinical relevance than the traditional facial sting test since it allows for assessment of a broader range of reaction patterns following product application, minimizes seasonal variability, and enhances reproducibility. DISCUSSION Sensitive-skin speciality panels developed in this manner can be used to predict the value of finished products in a human model with more relevance than patch testing, repeat insult patch testing (RIPT), cumulative irritancy testing, or the chamber scarification test. The concept of "sensitive skin" is useful since these individuals may possess one or more of the following anatomic cutaneous changes: heightened neurosensory input, enhanced immune responsiveness, and/or diminished barrier function. Heightened neurosensory input represents an augmented response to otherwise minor cutaneous stimulation. Sensitive-skin patients may have altered nerve endings, more neurotransmitter release, unique central information processing, chronic nerve ending trauma, or slower neurotransmitter removal to account for this reaction. Enhanced immune responsiveness is a second contributing component of sensitive skin, consisting of heightened antibody response to antigen presentation. This may be man- ifested in several different manners such as immunologic contact urticaria, allergic contact dermatitis, or atopic dermatitis. Such patients demonstrate increased positive reactions to patch and prick testing, with the height of immune responsiveness occur- ring around age 30 and progressively decreasing thereafter. Lastly, defective barrier function is an important component of sensitive skin. Lack of an intact barrier can result in heightened neurosensory input by inadequately protecting nerve endings and can also contribute to enhanced immune responsiveness through altered percutaneous absorption. This facilitates increased antigen access to the dermal vasculature and antigen-presenting cells. The permeability barrier resides in the stratum corneum of the epidermis and requires the presence of intercellular lipids, such as cholesterol, ceramides, and free fatty acids, acting as liquid crystals. It is alterations in this basic structure that cause patients with pre-existing clinical or subclinical derma- tologic disease (seborrheic dermatitis, perioral dermatitis, atopic dermatitis, eczematous dermatitis, or psoriasis) to present with sensitive skin. In summary, cosmetic and skin care product formulation considerations for sensitive skin include products with a paucity of ingredients, absence of sensitizers, minimum

PREPRINTS OF THE 1996 ANNUAL SCIENTIFIC MEETING 275 number of irritants, and absence of cutaneous sensory or vasodilatory stimulants. Sen- sitive-skin products can minimize potential problems by including anti-inflammatory agents, improving barrier function, and creating an exogenous barrier. REFERENCES (1) F. A. Simion and A. H. Rau, Sensitive skin, Cosmet. Toiletr., 109, 43-50 (1994). (2) S. Amin and H. I. Maibach, Cosmetic intolerance syndrome: Pathophysiology and management. Cosmet. Dermatol., 9, 34-42 (1996). (3) A. Fisher, Cosmetic actions and reactions: Therapeutic, irritant, and allergic, Cutis, 26(1), 22-29 (1980). Stability of dihydroxyacetone in self-tanning cosmetic products ASIRA OSTROVSKAYA, ANTHONY D. ROSALIA, PETER A. LANDA, and DANIEL MAES, Estee Lauder Inc., Research and Development Center, 125 Pinelawn Road, Melville, NY 11747. INTRODUCTION Dihydroxyacetone (DHA) is commonly used as a self-tanning agent in cosmetic prod- ucts. We have found that during its shelf life, DHA may release trace amounts of substances that can cause skin irritation or dermatitis (1). For this reason, DHA deg- radation has become a great concern to us and the industry as a whole. We have found that under certain uncontrolled conditions DHA can degrade, with the subsequent formation of formaldehyde, formic acid, and acetic acid. The levels of these three can be indicative of the extent of DHA's degradation. To determine and quantitate the possible degradation products of DHA, we at Estee Lauder developed modern analytical techniques and used them further to prevent and control DHA degradation. METHODS FORMALDEHYDE When applicable classical methods employing derivatizing agents such as Nash's reagent (2,3) or 2,4-dinitrophenylhydrazine (4) are used for the determination of free formal- dehyde in the presence of dihydroxyacetone, erroneous results are obtained. Therefore,