THE INTERACTION OF DETERGENTS AND THE HUMAN SKIN 7 does not constitute definite proof that the wet work was the cause of the eczema. These objections, valid though they may be, sound somewhat far fetched, and so I too was rather startled when the experiments of Suskind et al (8) became known. Suskind et al (8) (after previous work by Jambor (9), which already had pointed in this direction) hospitalized a number of patients with eczema of the hand and, as the only additional measure, one hand was immersed twice or six times daily in a solution of a synthetic detergent or a soap, in a suitable concentration. The other hand served as a control, and was im- mersed for the same time in tap water. 23 normal subjects were exposed to the same procedure. Contrary to expectations, not least of all of the experimenters--in most patients both hands improved equally, as can be seen from Table I (8). Table I Summary of observations: Household washing products Number of subjects 1 Test and control hands improved 49 2 No change in test or control hands 31' 3 Test hand unchanged, control hand improved 1 4 Test hand improved, control hand unchanged 2 5 Test and control hands worse 3 6 Test and control hands worse in first week of test but improved in second week Test hand worse, control hand improved or unchanged 3 7 o *Fifteen of these were subjects with normal hands. 89 In my opinion, this experiment, although it does not give us the right to extend its results to all detergents, opens up wide the question whether detergents and/or water damage a normal or eczematous skin. Moreover, it stresses once again the favourable influence of hospitalization itself on various skin conditions--a so called sanatio spontanea nosocomialis. It remains possible that the favourable influence of the hospitalization in Suskind's experiments more than compensated for the unfavourable in- fluences of the detergents. Whatever the final explanation of the facts observed by Suskind proves to be, it remains desirable to study the interaction of water, detergents and skin. Furthermore, it remains necessary for the manufacturer of a nex

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS detergent to screen his product with the utmost care for possible sensitizing or irritant effects. Dermatologists must invent tests to make such screening possible. These tests should have a high predictive value and be as easy to perform as possible. To design such tests, the dermatologist must consider what we know about the physiology and anatomy of the skin and the factors contributing to its optimum state. He then has to look for weak points in the defence mechanism. I need not remind you that the organ with which we are all concerned, and which has a surface of 1.5-2m2, is very thin. Starting from the surface, we find the epidermis and under it the corium above the subcutis. The epidermis, the principal topic of our discussion tonight, varies in thickness from about 0.1-0.4mm. It would carry us too far to discuss this whole thickness of the epidermis in any detail. We need only mention briefly that the epidermis is composed of the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum germinativum. It must be kept in mind that these layers are not equally well developed every- where. The stratum spinosum and stratum germinativum together form the Malphighian layer. Our chief interest tonight is the stratum corneum, which varies in thickness from 0.006-0.08mm. Kligman (10) in his des- cription of the stratum corneum stressed the importance of this re- markable layer. He pointed out that it is thanks to this "miracle wrap" that man can live on dry land, and that it prevents the penetration of noxious substances into our "milieu int•rieur". Kligman certainly exag- gerated when he stated in another place that the Malphighian layer is only of interest as the producer of the stratum corneum. This Malphighian layer certainly has its own physiology and pathology. On the other hand, it must be conceded that damage to the Malphighian layer is often due to the defects in the protection provided by the stratum corneum. The remarkable stratum corneum originates from the cells of the Mal- phighian layer by keratinization, a complex intracellular process. It would however, be erroneous to think that the stratum ½orneum consists ex- clusively of keratin. Szakall (11), and Spier and Pascher (12) showed that up to 20-40% of the stratum corneum consists of water-soluble substances, the greater part being amino-acids. These water-soluble substances proved to be markedly hygroscopic and are considered to be important for keeping the stratum corneum supple. They are also supposed to play a part in neutralizing alkali on the skin. The conclusion that the stratum corneum is an important barrier