3O JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Unnas' shake lotions are ageless and still used but calamine lotion, like Cinderella, is now transformed under the magic wand of cosmetic emulsifier and colloid mystique, technically described by Wells and Lubowe (1), to parade unrecognized in many creams, liquid face powders, compacts and other make-up preparations of the beauty parlour. New topical applications, however, have not solved many of the problems of treatment and some have brought new difficulties. Discussion of some of these, with cosmetic chemists and a clinical dermatologist meeting on common ground, may be mutually helpful. THE CHANGING SKIN Generally speaking, except for common skin diseases such as bacterial infections, infestations, contact dermatitis, etc., most topical treatment is used to remove or ameliorate a symptom. This symptom can be an expression of a systemic illness, but more often it is just a temporary functional variation from the physiological mean, as in epidermal keratinization and dermal functions involving sweat and sebaceous glands (including ache and seborrhoeic conditions), pigment formation, vascular activity including, for instance, frictional urticaria (dermographism), hypersensitive reactions to cold ("white fingers", chilblains), and other individual responses to radiant energy and the environment. These normal variations in personal physiological function or reaction to environment only require treatment when such factors produce temporary symptoms. A grosser disturbance of function from the mean may cause a sympto- matic but still only temporary state of inflammation from which recovery soon or gradually occurs. In those in whom the skin is genetically pre- disposed to be "an inferior organ" epidermal functions such as keratini- zation, or dermal functions such as sweating, or others may be so disturbed that the skin recovers only slowly, if ever, as in chronic eczema and estab- lished psoriasis. These patients may require continued symptomatic emollient and anti-inflammatory treatment. Greater emphasis should be placed on the prophylactic treatment of these constitutionally inferior skins before such chronic functional disturbance occurs. The problem is more complex because in all persons the physiological or enzymic function, biochemistry and often the anatomy varies considerably from area to area. As illustrations, skin grafted from the thigh to the forehead always remains as thigh-type skin in its new position the cycle of hair growth varies

SOME DIFFICULTIES OF TOPICAL TREATMENT IN DERMATOLOG¾ 31 itch sensitivity varies moles and papillomas become tag-like or peduncu- lated on such areas of skin as the eyelids, neck (as seen in menopausal women), groins and axillae simply because, in some way, the skin is different there. Absorption of medicaments is also much influenced by the thickness of the horny layer as on the palms or soles compared to thin facial or flexural skin. The fundamental biochemical and enzymic differences, however, have still largely to be determined. DISORDERS OF KERATINIZATION The integrity of the main epidermal barrier (the stratum corneum) depends mainly upon the intact linear protein (keratin) chains and their firm cross4inking by the strong disulphide (cystine) and weaker hydrogen and salt links of individual amino acids. The protein manufacture in the lower viable epidermal cells, and the degradation in the outer dead horny layer is enzymically determined. The integrity, however, also depends upon an adequate water content replaced from sweat in and between the keratin chains to keep the skin supple, in turn protected by a layer of oily sebum which prevents evaporation. Patients with inherent abnormalities of keratinization, and varying capacity to retain water, are particularly liable to functional disturbance from physiological, environmental or disease factors. They may be seen as a spectrum from severe types of ichthyosis, the harlequin foetus whose skin is incompatible with life, through grades of ichthyosis to the milder forms as seen in most atopics (subjects of the eczema-asthma-hay fever- syndrome) and senile skins, to mild skin xerosis and keratosis pilaris where the defect is seen like a nutmeg grater at hair follicles of the arms and legs. The group to be treated also includes dry states of the skin con- valescent from inflammations such as eczema. These skins make up a large community who often require topical symptomatic therapy. THE HYDRATION OF KERATIN Reduction of water content by evaporation or climatic conditions when a cold dry spell causes a rise of barometric pressure and dew point (where gaseous moisture condenses) produces dryness, chapping, and stiffening of the keratinous horny layer in these susceptible skins. In the background parade many minor disorders. Among these are the superficial dry flaky eczemas of the face, pityriasis alba (the "tetters") as in children, chapping of wrists or hands especially where wet work increases evaporation, as in housewives or behind the knees in children,