The imidacloprid active ingredient is considered by the World Health Organisation to be moderately toxic. In laboratory animals, symptoms of acute (short term) oral exposure to imidacloprid included apathy and laboured breathing which lasted for five days. The LD50 for imidacloprid (an oral dose that results in mortality to half of the test animals) is 450 mg/kg body weight in rats and 131 mg/kg in mice. The 24-hour dermal LD50 in rats is >5,000mg/kg. It is considered non-irritating to eyes and skin from tests on rabbits10.
Symptoms following acute exposure to the agricultural imidacloprid formulation (imidacloprid and inert product) included reduced activity, lack of coordination, tremors, diarrhoea and weight loss. Some symptoms lasted up to 12 days after exposure, twice as long as the symptoms of exposure to the active ingredient imidacloprid alone11.