Would you wear a poison necklace.
That's nothing but fearmongering. Chemical sprays are sometimes necessary for humans in insect infested areas, so yes, I would rather use small amounts of chemicals than take my chances with the diseases and parasites that can be caught from insects such as fleas, ticks and mosquitoes. I give my dogs heartworm medication for the same reason. It is
a poison, but rather that in minute amounts than the alternative.
To shun slight amounts of chemicals in favor of taking chances with disease seems to be going backwards. Dogs (and humans) once had secondary illnesses from these parasites in droves, and fleas alone can transmit tapeworms, cause anemia, dermatitis, and rickettsiosis infections in dogs & humans.
To the OP: Yes, flea collars are fine, but like any treatment, it all depends on the brand. They contain the same chemicals as a spot on treatment would, and I've always used them to good effect, though I don't use them very often. If there is a reaction, they can be taken off immediately, and used temporarily such as if you are planning to walk a dog in the woods. If you have an infestation, though, topical treatments are probably better.