The animals are often immobilized in stocks from which only their heads protrude. They usually receive no anesthesia during the tests. After placing the substance in the rabbits' eyes, laboratory technicians record the damage to the eye tissue at specific intervals over an average period of 72 hours, with tests sometimes lasting 7 to 18 days. Reactions to the substances include swollen eyelids, inflamed irises, ulceration, bleeding, massive deterioration, and blindness. During the tests, the rabbits' eyelids are held open with clips.
Many animals break their necks as they struggle to escape.
The results of eye irritancy tests are questionable, as they vary from laboratory to laboratory-and even from rabbit to rabbit. Acute Toxicity Tests Acute toxicity tests, commonly called lethal dose or poisoning tests, determine the amount of a substance that will kill a percentage, even up to 100 percent, of a group of test animals. In these tests, a substance is forced by tube into the animals' stomachs or through holes cut into their throats. The LD50 testing period continues until at least 50 percent of the animals die, usually in two to four weeks. Like eye irritancy tests, lethal dose tests are unreliable at best.