Long story short: DO NOT USE HARTZ PRODUCTS. According to the Small Animal Hospital here in Amarillo, they see many cases where Hartz products are essentially poisoning animals. I have read an exorbitant of reviews on this product, and the effects range from skin irritation, shaking, vomiting, foaming at the mouth, seizures, to DEATH. Hartz has received more than 44,000 reports of adverse reactions associated with spot-on flea and tick products. For example, a man in Texas won a lawsuit against Hartz; his dog went into renal failure because of their products. Their statement was, “that’s the risk you take when you use our products”, “it was [the owner’s] fault he died”, and even “owner negligence was cause the death.” Any statement such as those above would not be issued by a company who values their customer base and truly is compassionate for animals. Please, spare your animals and use another product advised by a veterinarian. Know what you are giving your babies BEFORE you give it to them. I have, without a doubt, been touched by an angel.