SKIN REACTIONS TO COSMETIC PREPARATIONS 7 for her, she added that her skin reacted to the sand if she lay or walked on the beach. THE POTENTIAL IRRITANTS: (1) Physical: Light (sun) (heat) Temperature (cold) (dry winds) Moisture (rubber gloves) (dry cold winds) Mechanical - wool - friction, massage - scratching - plucking - picking - pore blockage - powders - Keratin Infection - bacterial - fungus virus (2) Chemical: Primary irritants: Chemical soaps, antiseptics, etc., Sensitizers A primary irritant is an agent producing dermatitis by direct action on all normal skin, if in sufficient concentration for a sufficient time. A sensitizer is a chemical substance which, after initial contact with the. skin following a latent period of 5 to 21 days, may on second contact, in reduced concentration on any part of the body, provoke specific changes. CROSS SENSITIZATION This means sensitization not only to the specific substance but also to other chemically related compounds. The chemical relationship may not always be obvious, as both the original compound and the secondary ones may undergo changes in the body producing a related compound. Even compounds which cannot themselves sensitize, i.e. hapten-like substances• may provoke reactions in persons sensitized to like chemicals. Thus a person may exhibit a tissue sensitization reaction to a compound which he has never met before, being sensitized to a related chemical. Sensitizatioa reactions may also continue long after all contact with the known sensitizer has ceased, owing to contact with related chemicals. The longer the contact with the primary sensitizer continues and the stronger the reaction, the more likely are secondary sensitization reactions to develop.

JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS This is not to be confused with the apparent sensitization reactions which toccur in the acute or generalized stages of a dermatitis. The irritable skin reacts briskly to almost any insult, yet when this acute stage is over a further patch test to the apparent sensitizer is negative. Cross Sensitization Groups 1. The "Para" group of hair dyes, e.g., pphenylene diamine with azo dyes in foods and pills, the colouring matter in brilliantine, leg paint, nylon stockings and hair nets (7), •vool, leather, the ink of ball point pens, and shoe polish (aminoazotoluene), local anaesthetics, pamino benzoic acid (sun fi!ters), the sulphonamides (including diuretics, diarnox, and antidiabetic drugs), and saccharin. The probable sensitizing product is a quinone, and in the case of pphenylene diarnine, quinone diamine. 2. Phenergan (promethazine)--pyribenzamine and pphenylene diamine. 30% of people subiect to phenergan sensitivity are also sensitive to pphenylene diamine, but paradoxically the converse does not hold good. 3. Balsam of Peru (found in some ointments, sticking piaster, fungicides, ointments and inhalations) is immuno-chemical!y related to the perfume, resins and balsams used in soap, to orange peel, vanilia, cinnamon and tar. 50•o of patients sensitive to balsam of Peru gave positive patch tests to soap perfumes, and 35% to perfumes and cosmetics (8). There may be cross sensitization between perfumes and citrus oils, and food and beverage flayours. 4. Synthetic oestrogens (dienoestrol, hexoestrol, etc.) and hydroquinone --monobenzyl ether (rubber anti-oxidant, rubber gloves, pigmenting agent for leucoderma), and the phydroxy benzoic acid compounds used in foods, drugs and cosmetics as preservatives (9). 5. Tetramethylthiuramdisulphide (soap antiseptic and axillary deo- dorant), and rubber anti-oxidants and rubber adhesives. 6. Rubber (sticking piaster) and other acrylic terpenes (essences of lavender, geranium, saffron and citrus oils). PREDICTION OF SENSITIZING INDEX The inclusion of new substances in cosmetic preparations should always be preceded by careful investigations and trial. It is unlikely that any substance will be included in sufficient concentration to act as a primary irritant. Potential sensitizers may be reduced to a minimum by animal and human skin testing. Any possibility of cross sensitization with known irritants would instigate the most stringent testing. Yet complete exclusion of all potential sensitizers is an impossibility, no matter how extensive the field trials are.