To make an adequate risk assessment or safety evaluation, it can be argued that a test
has to be performed in naïve human subjects. For this purpose, there has been a
number of sensitization tests designed. The most used is the HRIPT, originating
from a test described by Draize in 1944 (1, 12). The test includes subjects that are
exposed to the chemicals 9 x 24 or 48 h during a 3 weeks period. Following a 2
weeks rest period, challenge is performed on an exposed site and an unexposed site.
The challenge is performed using a 24 or 48 h patch test and the resulting reaction is
graded for clinical signs. The test can be performed in a variety of manners with
varying exposure time and occluding methods. The test is performed on a
comparative large group of subjects, typically around 100. Although the use of
human subjects for risk assessment is considered unethical and not recommended it
has been widely employed with claimed good result