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Pyrethrins



Natural pyrethrins from plant flowers are among the safest classes of
insecticides available. However, natural pyrethrins are light sensitive and
90% decomposition occurs within 15 minutes of exposure to a sunlamp.
Synthetic pyrethroids are more stable but also more toxic. They actually
are less dangerous if swallowed because the digestive tract can rapidly
toxify them, however, they are highly lipophilic and rapid adsorption
occurs following topical application. Toxicity in rats after topical
application is reported to be about 200 mg/kg which translates to about 14
grams for a 150 lb person.
Another problem is that other chemicals are sometimes added that decrease
the metabolism of the pyrethroids and this potentiates toxicity as well.
For an adult,  application to clothes and not the skin probably will  not
cause any problems.
Tremors and seizures are reported symptoms of toxicity. For animals that
show signs of toxicity after  "dips" the  treatment is to bathe the animal
well in a mild detergent or shampoo. Or, if ingestion has occurred to
administer charcoal and a cathartic.
Exposure to these chemicals would still be my choice.
D. Grove