Some of you may allready know the difference between Frontline flea products and others. I was a little worried recently because I didn't realise flea products can be so harmful to dogs and cats. My Aussie mix,Dodger has a severe flea allergy-he has to have Frontline. I looked up how Frontline works and found it does indeed work differently than others. http://frontline.us.merial.com/products/sub2_how.asp Notice it is absorbed into the oil glands and NOT the bloodstream,which would mean it doesn't hurt the kidneys and so on. Just a little info I thought was interesting,and gave me a peace of mind.