Pyrethrum and pyrethroids have little toxicity in humans.
Exposure to these compounds typically results in only an irritant effect on the ocular mucous membranes, first airways and digestive tract.
Neurological and pulmonary toxicity is also possible only for large quantities (also due to the presence of propellants and additives).
Pyrethrins are insecticidal compounds extracted from the flowers of Chrysanthemum cinerariaefolium (it is a perennial plant that recalls the daisy from which it differs for its deeply engraved, velvety, greyish leaves, almost all located at the base of the stem and for the unmistakable scent).
Pyrethroids are synthetic analogues of these compounds of natural origin.
Pyrethrins and pyrethroids are marketed in the form of powders, solutions, slow-burning spiral tablets and sprays. Toxicologically more dangerous solvents than the active ingredients themselves may be present in the latter type of product.
Synthetic compounds can be divided in turn into two groups: all those that do not contain a CN group (e.g. permethrin); all those that contain CN group (e.g. cypermethrin, deltamethrin, fenvalerate).
For pyrethroids containing a NC group, episodes of systemic toxicity characterized by paresthesias (secondary to sodium channel blockage), nausea, vomiting, fasciculations, mental state changes, coma, convulsions, pulmonary edema have been described.
The mechanism of action of these compounds results from their ability to inactivate sodium channels, blocking them in an open state.
As for compounds of natural origin, no cases of systemic intoxication are described. These compounds, however, in case of ingestion can cause nausea, vomiting, diarrhea.
In addition, the compounds of natural origin are sensitizing and can give serious allergy phenomena.