Asked a vet what the best flea prevention actually is - here's what they told me.

I’ve spent way too long and way too much money buying flea shampoos, sprays and collars that did absolutely nothing. So I talked to a vet and basically I was doing everything wrong. And I'm practically now an expert in fleas so I’m sharing in case it helps anyone else.

Avoid flea shampoos, powders, most sprays, traditional flea collars, and anything that says it’s "natural" or "herbal." They might kill some fleas, but they do nothing against eggs and don’t stop the “flea life cycle”.  

What does work: Vet prescription meds, these are pills you give your dog. They provide consistent protection, and are the safest option for most pets. Topical spot-ons (again prescription). These are the ones that you apply to the skin monthly. Make sure you do it properly.

Important notes: If you have more than one pet, do them all. Keep treating for 3 months, because you have to break the cycle of eggs and fleas. Cats can’t always have the same products as dogs. 

Finally I used an online vet to get the prescription pill method, it was called Vetster. It was $40 before tax. Still waiting for delivery. I will report back in 3 months. Obviously ask your vet before using anything on your pet.