J. Soc. Cosmetic Chemists 19 3-20 (1968) ¸ 1968 Society of Cosmetic Chemists of Great Britain The and interaction of detergents the human skin The 1967 Medal Lecture by PROFESSOR DR. MACHIEL K. POLANO, Department of Dermatology, University Hospital, Leyden, Netherlands, delivered before the Society of Cosmetic Chemists of Great Britain on 22nd March 1967, with Dr. A. W. Middleton, President of the Society, in the Chair. Synopsis•Contact eczemas are dealt with, particular reference being made to orthoergic eczemas caused by detergents. An improved washing simulator made it possible to distinguish between various detergents in respect of their capacity to wash out amino-acids, and to Mute "soluble proteins". The results of arm immersion tests are also discussed. Speculating on the characteristics of the distinguished Society before which I stand this evening, I have come to the conclusion that one of them must be a marked preference for variety. How could I otherwise explain that after such authorities as Sir Charles Dodds and Lord Todd you have invited me to deliver your third Medal Lecture. Needless to say I feel honoured and proud. It required no speculation on my part to find a field of common interest between you, as cosmetic chemists, and me, as a dermatologist. Travelling from different directions, we meet as our interests approach that very important organ, the human skin. I presume that you desire as much to complement your expert knowledge of chemistry with some knowledge of the biology and physio-pathology of the skin, as I feel a desperate need to know more about chemistry, to become a more efficient dermatologist. I have gained the impression from your Journal that you include detergents in your field of interests, and this led me to the choice of tonight's subject. May I start with a statement which sounds axiomatic: Detergents irritate a normal skin and unfavourably influence the course of an eczema. When I 3

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS started my training as a dermatologist, this statement could be regarded as a truism, but during the last decade we have gradually become aware of facts that require us at least to restrict, or even to doubt, its validity. I feel obliged to clarify the terms "irritation" and "eczema". To give a good definition of eczema is one of the more difficult things that can be asked of a dermatologist, even more so if he has only a very short time in which to discuss this question. One of the best definitions available is un- doubtedly that of Hebra: "Eczema is everything that looks like an eczema". This definition has only one drawback: it does not make us any wiser. Another difficulty is that the opinions of dermatologists differ on what should be called eczema and dermatitis. For the moment, the best we can do is say that "eczema" denotes a family of skin disorders that may, at the same time or at different times, show redness, little nodules (papules), vesicles or even blisters, and weeping or scaling. Under the microscope we see, as their pathological counterparts in the epidermis, cellular pro- liferation (acanthosis), oedema, spongiosis and vesicle formation and in the dermis- hyperaemia and cellular infiltration. To further delimit my position, I may state that this definition of eczema includes conditions which many dermatologists call dermatitis, dermatitis venenata, eczematous dermatitis, and many other names. This evening I will restrict myself to those types of eczema that are provoked by external causes, the contact eczemas. It is very important to distinguish two subspecies within this species: the eczemas caused by what we call a toxic influence, the orthoergic eczemas, and those caused by an allergic reaction to an external influence, the allergic eczemas. Both kinds of reaction are very important. When you wish to market a new product it should not possess sensitizing properties otherwise it might cause allergic reactions in some of the persons who use it. I will not go into this important subject, except to refer to the difficulties that have been caused by sensi- tization due to p-phenylenediamine hair-dyes and, more recently, by the tetrahalogenated salicylanilide disinfectants in soaps. You are undoubtedly aware of the fact that a typical characteristic of sensitization is that, as a rule, it occurs only in a few of the persons exposed to the material. Other agents may, when applied externally, cause reactions in every user. We call such reactions toxic, or irritations. As in every biological occurrence, susceptibility to toxic reactions varies between so-called normal subjects. This explains why some subjects are irritated by concentrations of a given substance that are innocuous for others. The important difference between toxic and allergic reactions lies in the fact that increased con-