In practice, a company which needs to classify a mixture (e.g. for skin and eye effects) has the following options:

• Generate new in vitro test data on the complete mixture: this takes time and can be expensive if companies have a lot of mixtures to classify.
• Apply the bridging principles: this can only be done if test data exist for a number of ‘reference mixtures’ from which bridging is performed.
• Calculate the classification using the additivity method. This is the easiest option, but it is also the most conservative one.