JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS of the dye behind her ear and asks her husband to inspect the result a few minutes later. As no reaction will be visible after this short time, she assumes that all is well and proceeds to dye her hair. She retires to bed, satisfied with her operation, but, in the early hours of the morn- ing, she wakes feeling as if her scalp was on fire. She is further alarmed by the fact that she can scardely open her eyes, due to the consider- able swelling of her eyelids. After an anxious night she then presents herself to the nearest skin clinic, where the dermatologist can usually make the •liagnosis as he passes her by. Similar reactions follow exposure to other agents and the site of the eruption may vary with the part of the skin which comes in contact with the offending substance. It should be remembered that thick- skinned areas are less likely to show inflammatory changes than are thin- skinned areas, such as the eyelids. It is quite a frequent experience, for example, to find a patient, sensitive to the dye in nail lacquer prepar. a- . tions, who never shows skin changes in the hands at all. The eruption is usually seen on the thinner skin of the eyelids, which may become quite swollen as a result of contact with the dye, brought about, for example, by the nervous habit of tapping or rubbing the lids with the fingers. Some primary irritants may in their turn become sensitising agents. A common example of this is seen in industry with chromium. Chrome ulcers or "chrome holes" are usually due to small amounts of chromic acid or other chromium salts which reach the living cells of the prickle layer through a small abrasion or incised wound in a worker's hand. -The presence of these salts produces a local painless ulceration of the skin which slowly enlarges unless the lesion is treated. Some individuals, however, subsequently develop a rash composed of vesicles which are intensely irritating, in the neigh- bourhood of and remote from the original chrome ulcer. They have become sensitised to chromium and then, wherever chromium comes into contact with their skin, they develop an irritating dermatitis. The mechanism involved in sensi- tisation is not fully understood, but it would seem that many substances have the property of forming loose complexes with the proteins in the skin of susceptible subjects. ,.This protein complex acts as an antigem Antigens are substances which in some way disturb protein synthesi s in the cell, so that antibodies are produced instead of normal proteins l )• Haurowitz mentions that the surface • of antibody molecules is adapted.:., complementarily to the determinantli: _ molecular groups on the surface of?i the antigert molecule. These appear•:•} to be strongly polar groups consisting:.:11i mainly of negatively charged acid!? groups. Such groups must posse ss' ' a deB. nite shape in order to causei.) sensitisation, thus Landsteinor has shown that the flexible parafftiY chain of a fatty acid cannot act as anl antigen. Furthermore, there always a latent period between thel 208

COSMETICS AND DERMATITIS contact with the antigen and the ment of sensitisation, during ich further application of the to the skin will produce no Obvious reaction. This period is about ten days and may be i shorter or Ionger. We are unable, unfortunately, to rmine in advance which 'sub- ta•nces are likely to produce sensiti- iSation, and except for the azo dyes and the amine intermediate dyes, we are not able to correlate sensitis!ng !properties with chemical structures. .It is therefore necessary to try out a preparation by patch testing several hundred normal people be- one can determine its sensitising { i•":i:Powers. In this respect it is worth •½/•1111:/:remembering that, if a substance produces a skin reaction in at least one in two hundred normal subjects, its cdmmercial development should not be proceeded with until a further test on two hundred more subjects :i}!.::'i:,11 :: has shown that the risk of sensitisa- tion is less than 0'5 per cent. Should this percentage be exceeded, a care- ful review of the composition of the cosmetic should be undertaken, to see which ingredient is responsible for sensitisation, and this should be excluded. Prophetic patch tests are undesirable in industry, however, even though they have been popular in the United States. Patch tests intended. to be carried out by the user at home are unlikely to be done properly, and in any case patch tests require skill and experience in their interpretation. (Continued on page 210) -x • .... CHROMIC ACID //I • PRICKLE / \ 0-.--* .... :'1'"-.'"' C[Lt_ NUCLEUS (-- Figure 5. Theory or sensitisation mechanism. Chromic acid in contact with skin protein on surface of a prickle cell. ELL RECEPTOF• Figure 6 (above): An antibody has been pro- duced at cell surface. Note diagrammatic representation of "complementary fit." Figure 7 (below): Antibody has united with antigen (chromic acid) leading to release of histamine and other substances. HISTAMINE RELEASE •,..r• 209