I just saw this and wanted to pass to all. I used Hartz Ultra Guard Flea & Tick on my 6 yr old MinPin “Mister”. I didn’t notice any problems but I not gonna use it anymore. I found this info on Wikipedia. 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 Industries to cancel uses of several flea and tick products containing phenothrin that were linked to a range of adverse reactions, including hair loss, salivation, tremors, and numerous deaths in cats and kittens. In the short term, the agreement called for new warning labels on the products.As of March 31, 2006, the sale and distribution of Hartz’s phenothrin-containing flea and tick products for cats has been terminated. However, EPA’s product cancellation order did not apply to Hartz flea and tick products for dogs, and Hartz continues to use phenothrin in a concentration of 85.7% in many of its flea and tick products for dogs.