British law says that any new drug used for medicine, must be tested on at least two different types of live mammal. One of these must be a large non-rodent type animal.
This is to make sure the drug works and doesn't hurt you.
Animal testing has also sometimes been used for developing:
Household products Agricultural chemicalsIndustrial chemicals PesticidesPaintFood additives
In some countries animals are also used to test beauty products. But this is not allowed in Britain anymore.