New approaches to the assessment of eye and skin irritation

Assessment of eye and skin irritation potential is an important part of any comprehensive toxicology programme for new chemicals and consumer products. The original skin and eye irritation assessment methods described by Draize et al. are still widely used for regulatory purposes with only slight modification. These methods have been re-evaluated in the light of the modern approach to toxicological testing requiring refinement of protocols, reduction in animal numbers, and replacement of in vivo tests by in vitro assays. A refinement in the original Draize skin irritation test accepted by regulatory authorities is reduction of test substance exposure time from 24 to 4 h. This makes the test less stressful. The Low Volume Eye Irritation Test is also a less stressful, more predictive refinement of the Draize eye irritation procedure. Many in vitro models are being developed for use in the assessment of eye and skin irritation potential in the hope that the animal tests may some day be replaced. In order for alternative tests to be incorporated into safety assessment, they must undergo a defined evaluation that allows toxicologists to determine whether the new procedures provide relevant information. As the validity of the methods is determined, the new procedures can be incorporated into safety assessment using a tier assessment process. The first step in tier testing is a thorough analysis of existing in-house and published data on the test substance or similar material. A review of physical/chemical characteristics can also provide valuable information. If more data are needed in order to complete the safety assessment, the next step is to evaluate the test substance in in vitro assays. The in vitro data may provide sufficient information to make a safety assessment. If additional information is required, then in vivo testing may be conducted using a limited number of animals or human clinical studies. If alternative procedures are to be ultimately accepted for use in safety assessment, regulatory authorities must become active participants in programmes designed to assess and validate the new tests.