The impact of atopic status on a predictive human test of skin irritation potential

There has been much interest in recent years in the replacement of the Draize rabbit skin test for the identification of chemical skin irritants. A considerable effort has gone into the development of cell culture based assays. However, where ethical and safety considerations permit, the most obvious alternative is to use man himself. Data obtained using a suitable assay based on the endpoint of concern in the species of concern should be accurate and will represent a vital data base on which to develop sound in vitro assays. Thus, it is important to ensure the data produced in human assays is representative for man generally. To this end we have chosen to examine a number of variables and in this work report the effect of atopic status on the results obtained in a recently described human 4-h patch test. 30 atopic (defined by specific IgE to common allergens and by elevated total IgE) and 28 non-atopic volunteers were tested in this human 4-h patch test using 20% sodium dodecyl sulfate (SDS), 10% hydrochloric acid (HCl) and undiluted cocotrimethyl ammonium chloride (cocoTAC). The level of irritant reaction was higher for SDS in the atopic panel, but was similar for HCl and cocoTAC. The rank order of irritancy was the same in both panels. The results indicate that, whilst the intensity of reactions may be higher in atopics, their pattern of responses is similar to non-atopics. There is no evidence to indicate that they should either be deliberately included or excluded from the test panels recruited on a routine basis.