How long does it take for dog and cat flea products to work?

I have 5 cats and 2 dogs. They are all infested with fleas really bad. I just purchased the “HARTZ” brand of once a month drops for all of them. I was wondering if anyone knew how long it takes for it to take effect.
I just gave the animals their first treatment 2 days ago , and they are still badly infested with the fleas.
2 of the cats seem to be very sick over this, they are getting very skinny. I have no other means of money, as I have spent my last penny on this product, so I don’t have the finances to be taking them to a vet.
I was just wondering if maybe it takes time to get rid of the fleas. I expected them to be gone instantly with this product.
Obviously i was wrong.
CAN SOMEONE PLEASE PLEASE HELP ME WITH THIS!!!??????
To be more specific, I bought “Hartz control, once a month drops”, the one where you apply it their back between their shoulder blades.
Hopefully someone can help me, as I love my animals very much and can’t stand to see them suffer.

Hartz not only won’t kill fleas, it will harm animals, and it can kill cats. That may be why your cats seem sick and aare getting skinny — it may have damaged their kidneys.

The only effective and safe flea treatments are Frontline, Advantage, and Sentinel. Use the type for cats on cats…you can use cat medicine on dogs but not the other way around.

A dose for a cat or a dog under 30 pounds costs about $13.00 and lasts a month. Advantage works faster than Frontline…I have seen dead fleas dropping off a cat within 15 minutes. That may sound more expensive than stuff you can buy at a pet, feed. or grocery store, but they actually work and won’t harm the animals.

I would take the Hartz stuff back to where you bought it, tell them it doesn’t work, and get your money back.

Looking for an effective flea treatment, find it here .