THE INTERACTION OF DETERGENTS AND THE HUMAN SKIN centrations of a so-called toxic substance may cause a reaction in everyone, whereas allergic reactions depend in the first place on an immunological process, in which concentration plays only a secondary role. Another important fact to bear in mind is that although some irritations may cause eczema--a so-called ortho-ergic eczema--not every result of irritation is called "eczema". It must be admitted at once, however, that it is a difficult and often purely subjective matter to draw the line between "simple" skin irritation and an "orthoergic" or "irritative" eczema. Let me dwell for a moment on the words "toxic reaction" and "irrita- tion" In a wide sense, every adverse reaction directly caused by some substance is toxic, but in common parlance the term "toxicity" is often limited to the more serious reactions and "irritation" to the less severe everyone will agree for instance, that skin necrosis caused by a strong alkali or acid is toxic. Moreover, such a reaction is not an eczema. A little scaling or redness of the skin caused by the same substances in high dilu- tions is adequately described as irritation, and only a few would call them eczema. I hope I shall not confuse you by telling that van der Meiren and Achten (1) succeeded in provoking a condition that had all the patho- logical symptoms of eczema, by applying to the skin of normal persons a carefully chosen concentration of a potassium hydroxide solution or sul- phuric acid, both substances causing necrosis in higher concentration. After this introduction, I can more easily approach the subject of this evening: the pathogenesis of conditions caused by detergents and having the symptoms of a "simple" irritation or of an orthoergic eczema. It has already been mentioned that some doubt had arisen as to whether deter- gents cause eczema or skin irritation at all and, if so, what pathogenesis is involved. I will also report on a related subject, the results of investigations into what happens in a skin exposed to detergents irrespective of whether such exposure leads to pathological effects. May I go back to the question---do detergents irritate a normal skin or deteriorate the condition of an eczema? If the answer to this first question is in the affirmative, we shall have to consider which class of detergents is the worst offender. Then we must consider the question of how to choose from a series of new detergents those that are the least liable to give un- desired reactions. It can be easily demonstrated that positive reactions can be obtained in man by patch-testing with soaps or syndets in various con- centrations. The same holds for experimental animals. Because the con- centration of the detergents and the kind of contact in patch-testing is quite different from the conditions existing under normal use of these

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS detergents, these positive patch tests do not give conclusive evidence that the "normal" use of a detergent will cause undesired effects. One of the conditions attributed by Jacobi (2), Bettley (3), Cooke (4), and others to the use of detergents is a so-called chapped skin. This condition was described earlier by Gaul and Underwood (5). It consists of a rough, scaling skin with superficial fissures in the stratum corneum reaching into the rete malphighi. The original authors attributed this disorder to changes in atmospheric conditions, such as occur in sudden drops of the dewpoint. They considered the principal cause to be loss of water from the stratum corneum. At this point I want to stress the fact that "dry" is not only the opposite of "fatty" but also the opposite of "wet". Already in 1952, Blank (6) pointed out that callus becomes brittle in a dry atmosphere and becomes supple again when it is allowed to take up water the cosmetic industry recently seems to have appreciated this fact too. Many advertise- ments at present stress, as an advantage of certain creams, that they bring moisture to the skin. Formerly, it was more usual to emphasize the fat content. I will not at this moment bring up the question of whether it is possible to introduce moisture into the skin directly, or whether the ad- ministration of emulsifiers is more advisable when we want to make a brittle skin supple again. At this point in our discussion we come to the second question--whether chapped skin may be caused by detergents in addition to atmospheric conditions. Theoretically it is not unlikely that the answer to this question could be affirmative, because detergents are able to leach out substances from the stratum corneum that normally bind water. But the only definite proof would be the observation of chapped skin caused, beyond any reasonable doubt, by detergents. This proof is lacking for the moment. Carter and Griffith (7) while observing the skin of housewives exposed to various detergents, found a marked correlation between chapped skin and meteoro- logical conditions, but stated that the additional effect of water and detergents in causing chapped skin was slight. If we turn to the question of whether water and detergents may cause eczema, we find that most people, and doctors as well as patients, are con- vinced that this is so. We must now examine the evidence brought forward to support this contention and see whether it can withstand criticism. Arguments in favour are the "observation" that much wet work may cause or worsen eczema, and that stopping this work is followed by improve- ment. Now, the fact that cessation of wet work is followed by improvement