188 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS The list of drugs with recognised photosensitizing properties has lengthened considerably in the past decade. Nearly two years ago, a number of dermatologists in England noted a group of patients with an unusual pattern of dermatitis, for which they could find no ready explanation. The clinical picture was more or less identical in all the patients, making them recognisable with ease. Their skin eruption came on relatively suddenly, usually in persons who had no previous history of eczema or dermatitis. It consisted of a diffuse redness affecting the whole of the head and neck areas, including the forehead, eyelids, in and around the ears, and the neck down to the collar line. The webs, sides and backs of the fingers and hands, as well as the backs of the wrists and forearms were often involved. It was sometimes accompanied by considerable swelling, particularly of the eyelids and of the loose tissues of the face. Some areas developed blisters which would burst and produce considerable serous exudation, which was followed by crusting, fissuring and dry scaling. The main symptoms were a burning sensation, soreness, and irritation. Although occasional patients showed a more widespread eruption, in the vast majority it was confined to the light exposed areas of the head and neck and the hands and forearms. The sharp limitation at the collar line or the "V" of the front of the neck in men who wore open shirts, or a deeper "V" in women corresponding to the shape of their dresses, were persistent and striking features. We felt no doubt that this pattern of dermatitis had a close association with light, although paradoxically we were seeing most of them in December, January and February of an Enghsh winter! We carried out a number of skin tests and other investigations without gaining any clue. The majority of the patients were men, but a few women were also affected. Their occupations varied and, in fact, almost none of the patients believed that their work was responsible. The problem was solved, however, principally by the detailed investigation of an "epidemic" of patients with this dermatosis seen by Wilkinson • in an engineering factory at Maidenhead. While looking for fluorescent material in the factory which could give a clue to a photosensitizing substance, he found in a very thorough study that a solution of the toilet soap from the wash rooms fluoresced. Although he did not perhaps at once appreciate the significance of this fluorescence, the immediate co-operation of the research department of the soap manufacturer laid bare the whole story. A new chemical germicide, tetrachlorosalicylanilide, had been intro- duced by one large soap manufacturer some months before into two of their toilet soaps and by other manufacturers into a number of toilet goods. (The germicide had only been incorporated in the soap for a period of three months when continuing research by the manufacturers suggested

PHOTO-CONTACT DERMATITIS FROM SOAPS 189 a potential hazard, and production of new tablets had already ceased before Wilkinsoh's request for assistance in connection with the factory at Maidenhead.) Although an advertising campaign indicated that the form- ulation of two widely used soaps had been changed, I believe it true to say that no more than one or two dermatologists were aware of a change, or appreciated that it could be significant. The main reason for this failure appeared to be that dermatologists, in this country at least, do not think that toilet soaps are causes of allergic sensitivity reactions. In Denmark, Hjorth • has shown that soap perfumes may produce reactions in patients primarily sensitized to Balsam of Peru, but the latter is used much more frequently there than in Great Britain. On going back to question all the patients we had previously seen with this striking clinical picture, we found that virtually all of them admitted to having used one of the toilet soaps which we now knew to contain tetra- chlorosalicylanilide. However, we have since seen a number of patients who appear to be typical cases, but who deny that they have used any of these soaps. One knows, of course, that patients are fallible and some may not know what soaps they have used. Presumably most of the patients affected used the same soap for bathing as they did for washing their face and hands, and hence it was puzzling that the covered parts remained so completely spared more so because some patients readily reacted to a skin test with the chemical on their backs. When carrying out patch tests with a photosensitizing substance special precautions are needed. The tests should be duplicated so that one can be exposed to light and the other used as a control. In these patients, my method was to test with tetrachlorosalicylanilide as a 1% solution in methyl ethyl ketone, applying two identical patches on the skin of the back. They were left in place for fortyeight hours, after which they were removed and any positive results recorded. If the test was negative, one patch was covered with black paper and the other irradiated (over a wider area than the actual test site) with a suberythema dose of ultraviolet light from a Hanovia mercury arc lamp. In practice, an exposure of thirty seconds at a distance of thirty inches was found to be adequate. The results were then recorded after a further fortyeight hours. If both tests were positive fortyeight hours after first application, no light exposure was usually given. The results showed that about one-third of the cases gave a positive patch test at the fortyeight hours or ninetysix hours reading, without the addition of ultraviolet light, but that about two thirds of them required the addition of the light exposure to obtain a positive test. It is surprising that the patients who gave a positive test without exposure to light, did not produce dermatitis on their trunks when bathing with ,the soap containing the chemical.