The test substance should be applied uniformly over an area which is approximately
10 % of the total body surface area. With highly toxic substances the surface area covered
may be less, but as much of the area should be covered with as thin and uniform film as
possible. Test substances should be held in contact with the skin with a porous gauze dressing
and non-irritating tape throughout a 24-hour exposure period. The test site should be further
covered in a suitable manner to retain the gauze dressing and test substance and ensure that
the animals cannot ingest the test substance. When testing solids, which may be pulverised if
appropriate, the test substance should be moistened sufficiently with water or, where
necessary, a suitable vehicle to ensure good contact with the skin. When a vehicle is used, the
influence of the vehicle on penetration of skin by the test substance should be taken into
account. Liquid test substances are generally used undiluted.