Phenothrin, also called sumithrin, is a synthetic pyrethroid that kills adult fleas and ticks. It has also been used to kill head lice in humans.

Phenothrin is often used with methoprene, an insect growth regulator that interrupts the insect’s biological life cycle by killing the eggs.

In 2005, the EPA required Hartz Mountain Corporation to cancel uses of several flea and tick products containing phenothrin that may be associated with a range of adverse reactions, including hair loss, salivation, tremors, and numerous deaths in cats and kittens. In the short term, the agreement calls for new warning labels on the products.

• Hartz Flea and Tick Drops for Cats and Kittens to be Cancelled, US Environmental Protection Agency
• Phenothrin and s-Methoprene; Product Cancellation Order, US Environmental Protection Agency
• Phenothrin; Amendment to Terminate Use, US Environmental Protection Agency
• Hartz product use recommendations
• Hartz-EPA agreement letter
• External MSDS

• Pyrethrins and Pyrethroids Fact Sheet – National Pesticide Information Center
• Pyrethrins and Pyrethroids Pesticide Information Profile – Extension Toxicology Network

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