Skin Sensitization: Strategies for the Assessment and Management of Risk

D.A. Basketter


The British Journal of Dermatology. 2008;159(2):267-273. 

In This Article

Risk Management

Risk management represents in a sense the final resort; when the sensitizer cannot be substituted or used at a safe level (a common occurrence in occupational settings), or when there has been a failure of risk assessment, then it is necessary to manage the risk for instance by communicating information and avoiding exposure by various means, including advice on personal protection.

The first level of this is the communication that a chemical represents a skin sensitization hazard, normally via a manufacturer's safety data sheet (MSDS) and appropriate labelling on the chemical container. In Europe, for skin sensitization, this means classification as 'R43: May cause sensitization by skin contact' in association with the St Andrew's Cross symbol:

However, under the Global Harmonization Scheme (GHS) being applied to toxicology, it is possible it will be replaced by the following symbol:

Whichever of these symbols is used, the message conveyed is very simple - the chemical is a skin sensitizer: avoid contact with skin. What is much harder to understand is whether this means that any contact may be harmful, such that wearing the protective equivalent of a space suit is necessary, or whether in fact it is only necessary to avoid regular and prolonged contact with high doses of the chemical. It is this lack of information that renders the risk manager's decisions almost impossible. Total avoidance of contact is difficult in almost all situations. In contrast, reducing exposure to an acceptable level can be achieved and will be more readily accepted by a workforce, thus enhancing compliance.

A basic enhancement of the information provided on an MSDS would be the provision of potency information, and for this purpose the type of scheme outlined in Table 2 might be highly appropriate. Clearly, a category 1 extreme skin sensitizer could be approached very differently to a material in category 4. At present, the EU proposal has been to identify three categories of sensitizer,[43] but within the GHS the current discussions are focused on just two, effectively attempting only to differentiate stronger allergens from weaker allergens. These actions are a good thing, but are extremely limited in scope when one considers that allergens vary by 4-5 orders of magnitude in terms of relative potency.[34,35,41,42]

There is one other important element of risk management: where a substantial number of persons has already become sensitized, then it may be necessary to provide different information and/or adopt additional measures. Action has been taken in the EU in this regard for both nickel[61] and for chromate,[62] where the aim has been not only to reduce the induction but also the elicitation of ACD.

A further example of this has come with the requirement in the EU to label cosmetics and detergent products for the presence of any of 26 fragrance materials. The burden of fragrance allergy in consumers was judged to be too high, with some work suggesting that perhaps about 2-3% of the general population were sensitized.[63,64] So, to aid the sensitized consumer, the threshold for labelling of these fragrances was set at 100p.p.m. for rinse-off products and at 10p.p.m. for leave-on products. In principle, the concept has been that those who are allergic to a particular fragrance chemical can now avoid the products which contain it. However, the practice of patch testing for all 26 fragrances has lagged some years behind the introduction of the labelling, so evidence of its benefit is currently limited. Furthermore, recent data indicate, as had been strongly suspected by some, that a good proportion of the 26 fragrances is not in practice common allergens, with some perhaps possessing little or no allergenic activity - see Figure 3.[65] It remains to be seen how the European regulatory systems catch up with the need to update this list, adding new allergens and removing those of little relevance. What would have been better was for an earlier proactive effort by this industry to lower the incidence of induction by improving their risk assessment and self-regulation, action that is now being implemented and which seems likely to provide a good model for other industries to follow in the future.[54,66]

Figure 3.

Proportion of a normal patch test population with allergy to the 26 fragrance allergens whose presence must be identified on the labels of cosmetics and detergent products sold in the European Union. The data are taken from Schnuch etal.[63]


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