Hen's egg chorioallantoic membrane test for irritation potential.

The increasingly large number of chemicals introduced onto the market and into the environment has necessitated the monitoring of environmental materials and specimen banking, as well as the development of rapid and reliable methods for the evaluation of toxicity. The Hen's Egg Test, or Hühner-Embryonen-Test (HET) is a rapid, sensitive and inexpensive toxicity test and can give information on embryotoxicity, teratogenicity, systemic and immunopathological effects, metabolic pathways and now, in developed form, on mucous-membrane irritation potencies of chemical substances. Testing with incubated hen's eggs is a borderline case between in vivo and in vitro systems and does not conflict with ethical and legal obligations especially animal protection laws. In the special field of mucous-membrane irritation testing, a specific score and classification scheme was developed for the HET, which allows risk assessments analogous to the Draize scheme. There is a good correlation between the results for HET tests on a variety of pyrithiones, phenols and isothiazolinones, and the corresponding data based on Draize tests. HET chorioallantoic membrane testing should and could not entirely replace current irritation tests in mammals, but it can diminish the number of investigations with mammals, as well as limit or eliminate pain and injury during animal experiments and allow regulators to set priority and toxicity categories.