Oh that is such a tough situation when you live in a tropical place with fleas everywhere.

Vets have told us that it's OK to keep using it on dogs with cancer, that the risks of disease from fleas are far greater than those of the chemical itself.

I have also been told by holistic practitioners that they would never use it, especially during chemo, because their immune systems are so compromised at that time and introducing additional toxins is asking for trouble. Have you asked your oncologist their opinion? I would love to hear what they have to say.

We have written about fighting fleas (in general) in our Nutrition blog :

"The Flea Dilemma for Cancer Dogs"

"Fight Fleas Naturally with Cedar Oil"

My personal experience has been that flea prevention starts with really excellent nutrition. Dogs who eat whole, healthy foods have stronger immune systems that fleas stay away from. The Flea Dilemma article talks about that.

After I got cancer, I started eating even healthier. I didn't use flea products anymore, and I never had another flea outbreak, even when I was in Florida for a few months. Our Tripawds Spokesdawg Wyatt Ray has never used chemical flea products and we've only found a tick on him once, and he's been to Texas where fleas are terrible.

Are fleas an issue right now? If so, I wonder if cutting back on the dosage just a bit, maybe a half-dose (the next dose down for a smaller dog, perhaps?) on your regular schedule, would still provide protection while allowing you to take preventative measures at home and with his diet? Just a thought, I've never tried that.

Hope this helps.