CONTACT ALLERGY 483 its structural formula is close to a known sensitiser in this respect the chances are even greater. Rook, Wilkinson and Ebling (3) give a compre- hensive list of known sensitising agents. It is sometimes suggested that animal experimentation should be used but this is unfortunately of very limited value. It is true that guinea-pigs can be sensitised to a wide range of chemical substances and any potential cosmetic which might be suspected of being a sensitiser could be applied to guinea-pigs and tested in this way. However, the fact that application to the guinea-pig results in no hypersensitivity cannot be taken to mean that humans will respond in the same way, and one is inevitably forced into some form of limited user trial. Sometimes, repeated, so-called prophetic patch tests on volunteers is advocated, but again this will detect only the most potent of sensitisers or those sensitised by other means, and it is not without ethical objections. The basic problem is that even with potent sensitisers one expects only perhaps 1 in a 1000 people to become sensitised in the normal course of events. If care and experience are used to select the ingredients of cosmetics, only the feeblest of sensitisers will escape the net and this implies that perhaps only 1 in 100,000 or less is susceptible. No form of artificial system can be expected to detect this level of occurrence. CONCLUSIONS Finally, I should like to pay a tribute to the cosmetic and toilet pre- paration industry. In spite of the widespread and increasing use of such preparations and in spite of the improvements in them which recent years have brought about, there is no evidence of any increase in the incidence of sensitisation. The amount of trouble which they cause is really remarkably small and I have no doubt that this is due to the constant vigilance of the manufacturers. (Received: 1st August 1968) REFERENCES (1) Von Pirquet, C. Miinch. Med. Wochenschr., 30 (1906). (2) Gell, P. G. H. and Coombs, R. R. A. In Clinical aspects of immunology, Chapter 13 (1963) (Blackwell, Oxford). (3) Rook, A., YVilkinson, D. S. and Ebling, F. J. G. Textbook of dermatology, 9,: Appendix 1. (1968) (Blackwell, Oxford). DISCUSSION DR. D. SPRINT: You state that patch tests •vith soaps are difficult to interpret because soaps themselves have a mild primary irritating effect and the concentration

484 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of the sensitizer in the soap may be very low. I am inclined to add "it is therefore necessary to test the ingredients separately in appropriate non-toxic, but higher concentrations". What is your opinion about this? THE LECTURER: I am inclined to agree with you about inserting such a sentence. One of the reasons I did not do so was that there are so many ingredients in many of these cosmetics that it does become quite a labour. Also the exact composition of many of them is, as you know, not precisely known, but in general I would agree with this principle. MR. N.J. VA• ABBg: Do you accept the view expressed by Professor Kligman that there are all grades of "irritancy" between that of a definite primary irritant and of a true sensitizer? Would you also support his scheme of testing for sensitization whereby the skin is initially pre-disposed to react by treatment with a known irritant? Tn• L•-CTUR•R: I agree entirely that there is no distinction between an irritant and a sensitizer and, in fact, while some may be only irritants and some may be only sensitizers, there are many which are both. I disagree most profoundly that there is no difference between the body reaction to an irritant and the body response to a sensitizer. In fact, the differentiation is based on the body response rather than on the chemical concerned. I do not quite know how to take this idea of irritating the skin beforehand there is evidence that if you produce irritation beforehand, at the right time thereafter you can get an enhanced response but at a certain time. you can get a diminished response. In this respect you can also get a potent sensitizer masking the effect of a less potent one. DR. T. J. E•.•.•OTT: In the last year or two there has emerged a number of ranges of so-called hypoallergenic (or non-allergic) cosmetics, and I am wondering whether the incidence of either real or imagined allergy is more widespread than comes to the attention of the dermatologist. In other words, do women only go to the derma- tologist when they have severe incidence of allergy, and is there more widespread inconvenience due to the use of cosmetics than we know of? If one takes your tribute, then really there ought not to be a need for special brands of cosmetics which are not allergic--to me this seems to be an obvious contradiction? Tn• L•CTURER: This is a good point and I just do not know the answer. MR. J. M. B•.AIrEWA¾: With reference to Dr. Elliott's point, I think the answer may be in the market place. Are these cosmetics making any impact on the market? I rather doubt that they are making any spectacular inroads into normal cosmetics I believe they derive from the U.S.A. where there tend to be rather more hypo- chondriacs than there are in Great Britain. A M•MBER OF TI• Am)IE•CE: In Liverpool we have been making a survey of cosmetic contact eczema over the last three years, and we have found a fairly large proportion of patients who have had positive patch tests, particularly to lanolin and parabens. I think it is true to say that well over half of the patients have probably developed their sensitivity to these materials because they are basically eczematous subjects who have been using these substances in either topical steroids or other local preparations.