Histopathology examination showed respiratory tract irritation, bronchioalveolar constriction and lung oedema. Formaldehyde was irritating to the eyes, and aqueous solutions of formaldehyde (0.1% to 20%) were irritating to the skin of rabbits. Formaldehyde was sensitising in the guinea pig maximisation test and the local lymph node assay with mice. On the other hand,specially designed studies (IgE tests, cytokine secretion profiles of lymph node cells) did not reveal evidence of
respiratory sensitisation in mice.