My dog, who is treated for fleas 5 times a a year, and therefore "used" to flea products, had a HORRIBLE reaction to this flea treatment. My dog never had any bad reactions to Frontline or Advantage, but Panacur 3D is another story. Within 12 hours of application, my dog started itching like CRAZY at the application spots. But worse, 24 hours later, my dog started having panic attacks, panting horribly, acting extremely hyper active, scratching herself psychotically, etc. It was getting very scary. I bathed her to get the remaining Panacur 3d off of her immediately. I will NOT use this product again and I do NOT recommend Panacur 3D to anyone!