Why Dogs Take Flea, Tick & Heartworm Preventives — and Humans Don’t

Have you ever wondered why we give our dogs (and cats) flea, tick, and heartworm preventives but we don’t take them ourselves? After all, we walk in the same grass, hike the same trails, and mosquitoes bite us, too. Shouldn’t humans need the same protection? It’s a smart question, and one I’ve heard from pet parents more than once. The answer comes down to biology, risk, and how medicine works differently for us versus our pets. The Different Risks We Face For dogs and cats, the stakes are much higher. Heartworm disease, spread by mosquitoes, is a major threat that can lead to heart failure and death if untreated. Ticks transmit dangerous illnesses like Lyme and Ehrlichia, while fleas can cause allergic reactions, anemia, and tapeworms. For humans, the risk/benefit balance is different.

While we can get tick-borne diseases, most are treatable with antibiotics if caught early. Crucially, heartworms cannot survive in people, and fleas don't live on us the way they do on our furry friends. How the Medications Work Most flea and tick preventives are designed to target parasite nervous systems. These drugs lock onto special channels in the nerve cells of pests and because those channels are very different in mammals, dogs and cats can tolerate the medication safely. Heartworm preventives work by killing microscopic larvae before they can grow into adult worms. Because pets are so vulnerable to these parasites, these medications are a vital safety net. Clearing Up a Common Myth It isn't about lifespan; it's about biology. Drug safety is about how a body metabolizes medicine.

Think of it this way: Tylenol is safe for humans but toxic for pets, and chocolate is a treat for us but can be deadly for dogs.

Flea and tick preventives fall into the opposite category: safe for pets at proper doses, but simply not designed for the human body. What This Means for Pet Parents If you’ve ever thought about skipping a dose, remember these three truths: The "Invisible" Infestation: By the time you actually see a flea, an infestation has already started. One Bite is All it Takes: Heartworm risk exists even for indoor or city dogs; it only takes one mosquito.

Prevention vs. Treatment: Preventing tick-borne diseases is much easier and less costly than treating them after the fact. Final Thoughts We don’t take these medications ourselves because we don’t need them, but our pets rely on us to protect them. These preventives are one of the simplest ways to keep our four-legged friends healthy year-round. That little monthly dose isn't "just something the vet says"—it’s peace of mind in a package. Prevention isn’t just about pests; it’s about protecting the tail wags, the couch snuggles, and the happy, healthy years you share together.