3-phenoxybenzoic acid (3PBA) is the result of exposure to pyrethroid insecticides (pyrethrins). Pyrethrins are the collective name for a group of pesticidal compounds derived from pyrethrum flowers in the genus Chrysanthemum that includes permethrin, cypermethrin, deltamethrin, cyhalothrins, fenpropathrin and trihalomethrin. Pyrethroids are synthetic analogs of pyrethrins.

Pyrethroids may affect neurological development, disrupt hormones, induce cancer, and suppress the immune system.

Pyrethroids are axonic poisons that work by keeping the sodium channels open in the neuronal membranes. Inhaling high levels of pyrethrins or pyrethroids may bring about asthmatic breathing, sneezing, nasal stuffiness, headache, nausea, incoordination, tremors, convulsions, facial flushing and swelling, and burning and itching sensation. A 37-year-old woman died of cardiorespiratory arrest after shampooing her dog with pyrethrin shampoo. Individuals who have ragweed sensitivity are especially vulnerable to allergic reactions to these products. Mothers of children with autism spectrum disorder (ASD) were twice as likely to have reported using pet shampoos containing pyrethrins as those who had healthy children; the effect was most severe if exposure was during the second trimester of pregnancy. In addition, parents of ASD children have reported the first onset of autistic behavior after the use of pyrethrin insecticide sprays in the home.