ELI5: Why are there no once a month chewables to kill fleas and ticks for humans? If they’re safe and effective for our pets, why are they not safe and effective for us?

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We don’t have fur, and the drugs are designed to be in the oils of fur. There are anti-parasite drugs that work for both humans and animals, but they don’t stick around on our skin for very long.


FDA rules for animals that will be eaten are much stricter than the rules for pets. The flea treatments given to dogs and cats are not tested to the levels that would be required for drugs used on human patients. We don’t know the rate or severity of side effects, because we’ve never cared enough to do the very expensive testing required to find out. In other words, we know that all or almost all animals who take the flea treatments are fine, and that’s “good enough.” It wouldn’t be good enough for drugs taken by humans.


I’ve heard those flea pills described as “slowly poisoning” the dog/cat. The poison is very low-level, but it’s enough to make the dog/cat *poisonous* to fleas/ticks, which are (obviously) very small and thus more sensitive to smaller doses. Most of what I’ve read in this thread confirms that ELI5 explanation. We accept this tradeoff because dogs/cats have relatively short lifespans, and the cumulative effects of the poison don’t really manifest, usually, until the dog/cat is near it’s maximum lifespan anyway. Also, the tradeoff in improved daily quality of life for not being constantly infested with fleas/ticks is worth being slowly poisoned. Flea/tick infestations also bring risks of other communicable diseases, both to the dog/cat *and* to the human owner, which is another *big* part of that tradeoff. Anyway, most humans wouldn’t want to be intentionally poisoned, especially for something as rare and manageable as fleas/ticks. Note that we do poison ourselves for more serious problems (see: chemotherapy and cancer).


The answer is actually pretty simple. The *drugs* exist, they simply aren’t *sold* as human flea and tick medicine. Once a month chewable Flea and tick medicine will kill fleas on humans as well, but humans hardly ever get fleas, so why bother spending millions getting it approved for humans? Source: am vet


Safe and effective tests done on animal medicine is a pale shadow of those done for human medicines. Very limited testing is done for most animal drugs, generally unless it is a farm animal, it will have human medicines with the doses roughly right. In short, animal medicines are probably not going to usually kill your dog. They are nowhere near as safe.