320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS DISCUSSION MR. G. L. GARDEL: May I assume that your research was carried out on single products, and that you did not use them in combination with other materials? I have found, from experience, that this sort of behaviour can be expected with single products, but when they are mixed with other compon- ents in a perfume compound, there is no effect whatsoever. TI•E LECTURER: I agree with that experience, and there are several possible reasons for this. In the first place, the concentration of the product is appreciably lowered in this way. Another reason is that the process is not finished when the material is applied to the skin, is in fact just com- mencing. The product has to penetrate the skin to a certain extent and has to react with other organic structures. All these processes may be influenced or interrupted by the presence of, say, 99% of other materials. Even the way in which the material is applied, e.g. in a cream base, an alcoholic solution, etc., may have an influence on the dermatological response. MR. B. tz[. KINGSTON: IS it not possible that the presence of alcohols, normally present in perfume blends, will render innocuous the aidehyde and ketone sensitizers, due to the formation of aceta!s and ketals ? THE LECTURER: Yes. MR. D. BAss: Do you have any experience of perfumes irritating the eyes ? I think it is common practice to perfume eye lotions. There are certain detergents available for baby shampoos, that do not irritate the eyes or sting them. Is there a perfume that does not irritate the eyes ? THE LECTURER: I think this is quite another problem. You are dealing here with primary irritation, and this is essentially different to sensitization. Primary irritation is a more direct reaction on nerve endings and an effect which is reproducible by all humans. Sensitization is just an effect that occurs after repeated application of much lower concentrations that are not irritant as such, and only affect a small proportion of people--it is not the normal reaction. As far as the eye irritation is concerned, one experiences a feeling of pain in the eyes due to a difference in osmotic pressure and this will safe- guard the eyes against prolonged contacts with foreign materials. Even plain distilled water stings the eyes, because it is not isotonic. As far as the shampoos are concerned, I consider it better to have a shampoo that stings, rather than one that gives no pain but which might be harmful one is not warned in the second case and that may be much more dangerous. DR. J. H. }V[ERZ: Do you find that a whole group of sensitized people are sensitive to the same sort of materials, or is it a question of idiosyncrasy--one person may be sensitive to one thing and someone else to another.

CONTACT SENSITIZATION DUE TO PERFUMERY RAW MATERIALS 321 THE LECTURER: The reactions are completely individual. MR. J. •/[. BLAKEWAY: Do you have to screen guinea pigs for particular sensitivities, in the same way that you do human beings ? Are they more sensitive than humans, less, or do they have the same peculiarities ? THE LECTURER: In the case of guinea pigs and rabbits we use special strains which are pre-disposed for sensitization. The reactions of the indi- vidual animals of these strains are almost identical. In general, animals are less sensitive. MR. P. J. L. BONGARD : Has sensitization any connection with the pH of the skin ? THE LECTURER: It would lead me too far into medicine to answer this question. The pH can certainly be correlated with the occurrence of eczemateous reactions, but deviations from the normal pH of the skin belong to medicine. }V[R. O. }V[. HOWARD: Am I to understand that for your tests you select a specific number of people who are prone to sensitization ? THE LECTURER: Not in our tests, but there are investigators who are working in this way. MR. O. M. HOWARD: IS it correct to select a section of the community who are subject to allergic effects, for specific tests on sensitization ? THE LECTURER: In experimental work to study the theoretical back- grounds of contact sensitization the chance of achieving results is much higher in these pre-selected groups of test-people. In a group of normal people these studies are almost impossible from a practical point of view. DR. V. KLEIN: I assume that the normal method of determining sensitiza- tion is a patch test. THE LECTURER: Yes. DR. V. KLEIN: In carrying out the patch test, where do you determine the concentration to differentiate between a primary irritation and sensitiza- tion ? Some years ago one of our men, who developed a serious dermatitis, was sent to a specialist who carried out some 30 patch tests on his back with concentrated materials including aldehydes, alcohols, etc. As a result, almost all of the tests were positive but the man was certainly not sensitive to so many of the materials. Where do you determine the threshold ? THE LECTURER: By lowering the concentration. When we have positive reactions we reduce the dose and try to find a threshold. If this is 50 times or 100 times the normal use value in perfume compounds, then it may still be possible to use the product involved.