So I talked to my vet before buying bravecto she said it was good but she has had some cats reaction be bad because of it being so strong. So I gave it a try and let me tell you both my cats are inside and have flea allergies and this stuff works great. I did do a second does in 2 months because my one cat started scratching. But it does work great . One of my babies is a old girl who is supper sinstive to things and she has done great with it. Will be staying with this one for sure.