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| NIOSH Home > Safety and Health Topics >Skin Exposures and Effects >Occupational & Environmental Exposures of Skin to Chemicals- 2005> Abstracts |
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Prevention of Allergic Contact DermatitisJ.D. Johansen, National Allergy Research Centre, Gentofte, Denmark Skin contact with low molecular weight substances may lead to contact sensitization and allergic contact dermatitis, which is a common and potentially disabling disease. The main determinants of allergic contact dermatitis are the potency of the allergen, allergen concentration or dose per unit area, the frequency of application, allergen matrix and skin barrier function. It is well-documented that restriction of skin-exposure to contact allergens is a very effective way to prevent allergic contact dermatitis, as illustrated by the effect of reducing hexavalent chromate in cement and nickel release from metallic items designed to be in close contact with the skin. The concentration of an allergen that induces allergy is often unknown. Experiments in healthy volunteers have been used to assess sensitisation thresholds. However the value of such results is questionable for prevention of allergic contact dermatitis due to lack of relevance of the experimental conditions to the complex real exposure conditions, further such studies bear ethical problems. Predictive animal assays may be valuable for pre-marketing screening of substances, preventing strong allergens from entering the market or reducing exposure. On the other hand several examples exist where these tests initially have failed to identify the sensitization potential of a strong allergen, or where the risk assessment based on positive results have failed and the allergen has been launched to the market in far too high concentrations. The most recent of such risk assessment failures are the use of the preservative methyldibromo glutaronitrile in much too high concentrations in cosmetic products including liquid soaps, giving rise to an epidemic of contact allergy. The current risk assessment procedure is very theoretical and does not take into account the epidemiological evidence of contact allergy in the population. It is important that the end-point of prevention, that is clinical disease, is incorporated into risk assessment and risk management models. Using elicitation data to assess thresholds limits e.g. for legislation provides a tool that is relevant for the disease end-point and which has proved effective in the past. It will cover both secondary prevention, that is protecting individuals that have become sensitized from getting clinical symptoms, and primary prevention, that is prevention of new cases of contact sensitization in the population. In this way the burden of disease will be reduced immediately. Models should be developed to exploit elicitation data more systematically in prevention of allergic contact dermatitis. Further it is important to see risk assessment and management as a continuos process, where a post marketing epidemiological surveillance system should form the basis for evidence based decisions. Information about contents of allergens in consumer products and in the workplace is another important tool of prevention, both primary and secondary. The ingredient labelling of consumer products needs to be optimised, so that the most known allergens will be more easy to identify on the label. Further full ingredient labelling should be introduced for products used in the work-place to ensure correct diagnosis in workers with occupational allergic contact eczema and meaningful information to the sensitized worker.
Content last modified: 3 April 2005
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