Has anyone heard of safety studys about Bio Spot (and/or other flea medications?)?

Has anyone else heard horror stories about seizures? A vet tech told me today that she thinks Bio Spot isn't safe, but she didn't really have any specifics other than a couple of personal experiences. It didn't seem like proof to me. I'm just wondering if anyone else has heard of problems with Bio Spot. I usually use Frontline, but it is so expensive, I was looking for a cheaper, but safe! and good! alternative.
Links if you have them would be great!

ALL topical flea treatments are dangerous, whether store brand or vet brand. They can cause neurological damage, organ failure, cancer, and death. Here:

http://apnm.org/publications/resources/f...

Is a detailed explanation of why these products are so dangerous.

I do not use ANY flea products, there are natural shampoos and sprays made with essential oils like Neem and Tea Tree which effectively kill and repel fleas without any chemical additives.