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Fleas: The Infernal Itch

An army of fleas wreaking havoc on their new home... your pet.

If it's warm out, there are fleas. Fortunately for you, fleas like the warmest, breathing, walking creature to make their home and that is your pet and not you. Unfortunately, many pets are allergic to flea spit and they will get an itchy allergic reaction that will drive them (and you) crazy! When things get really bad, a blood transfusion is needed to keep the dog or cat alive long enough to get rid of the fleas (but that's usually just puppies and kittens). And if that weren't enough, fleas also are famous for carrying tape worm eggs that will give your pet foot long worms that live in and feed from the intestines (um... gross). In other words, fleas are bad.

In a hurry? Click here to jump to "What I would do for my dog". Click here for my over-the-counter supply list.

The Flea Lifecycle

Fleas marching in a line.

In order to understand how to get rid of fleas, it's important to understand their lifecycle. If you don't break the cycle, you're doomed to endless fleas on your dog (and couch, and car, and bed).

Once fleas become adults and start feeding on your pet's blood (that's a fleas preferred meal), they have a little romance and the females start laying around 50 eggs a day. Those eggs are slippery and slide off your dog where they end up in every crack and crevice or your home. About a week later, they hatch into tiny worms (larvae) that feed on the adult flea poop. In another week or three, they make a cocoon that is sticky like velcro. Nothing short of burning your house down (not a recommended treatment) is going to get the fleas in this cocoon stage. Don't bother with the powders, the bombs, and the fumigation. It's not going to get those darn cocoons.

The cocoon is where the little worm becomes an adult flea (think caterpillar to butterfly). In about a month or two, when the fleas are mature and something warm and breathing walks by, the fleas hatch from the cocoon, jump onto the warm breathing thing, have a big meal, and then go looking for their own romantic date to start the cycle all over again.

The important point of this: it takes about 2 months to break the flea life cycle by killing all the adults and preventing eggs from becoming new adults. The targets of all of the flea medications, flea powders, and flea bombs are the adults, the eggs, and/or the worms (larvae) depending on the medication you pick. Nothing's going to touch the cocoon. So while you're treating for fleas, there is a good chance you're still going to see some fleas in the first few months. It doesn't mean that the flea medications aren't working, it means that those cocoons are hatching and you're killing a brand new batch of fleas before they can start the cycle all over again.

The other important part: if you don't treat all the non-human, warm blooded animals in the house, it's not going to work.

What are the Symptoms of Fleas?

In some dogs and cats, nothing. They're not allergic to flea saliva (spit). Historically, flea allergic hunting dogs in the Southern United States were selected against for having flea allergies. Now we select for cuteness (and a shot at Instagram or TikTok fame). The result: more pets get to experience the misery of being constantly itchy.

When us people have allergies, we tend to get itchy eyes and sneeze. Dogs and cats get red, inflamed, and itchy skin all over. The first place this tends to show up is the ears (by way of an ear infection). The next place is the site of nonstop chewing and scratching everywhere their mouth can reach. Eventually hair loss, scabs, and some bad skin infections appear.

Ears: Dog and cat ear canals are a lot different than people. These pet ear canals go down, take a sharp turn, and then continue toward the head before ending in the (hopefully intact) ear drum. As a result, your pet's ear canals are already a more warm and humid place ready to host a yeast and/or bacteria party. If you turn up the dial just a little bit more by adding allergies, the party gets started. That's why veterinarians look for (or should be looking for) fleas whenever there is an ear infection. Read our Ear-Resistable post for more information.

Hair and skin: Your pet's reaction to itching is scratching. Who can blame them? Unfortunately, their mouth can only reach so many places! One of the easiest places for them to reach is the top, back third of their body, just in front of their tail. They will chew and nibble at this area trying to relieve the madness of constantly being itchy. Sadly, this just makes things worse as they eventually cause enough damage to the skin that they also cause a skin infection (dogs' mouths aren't the cleanest places on earth). The tell tale sign of this allergy is broken hairs or an area completely without hair everywhere their mouth can reach that is full of scabs and red, angry skin. Not many other things do this to a dog.

Butt: Remember that talk of tapeworms at the beginning? If you notice what look like bits of short grain rice stuck around your dog or cat's butt, there is a good chance they have tapeworms. And if they have tapeworms, there is an even better chance your dog or cat has fleas. The fleas pick up tapeworm eggs (those are what's inside that rice grain looking packet). The dog eats the flea. The dog gets tapeworms.

Pale, listless, poor doing puppies and kittens: These young ones don't have many reserves to begin with... they're newborns! It doesn't take a ton of fleas and tapeworms to steal enough blood and nutrients to cause a big problem.

Types of Flea Medications: some good, some deadly

We're going to talk active ingredients here. An active ingredient is the thing that makes the medication work. In most (but not all) instances, the brand name is just charging you more for the same ingredient. The reason this isn't true for all drugs is that some generics aren't mixed with the same other ingredients and just don't work as well (as is the case with one of the more popular heart failure medications for dogs).

Pyrethrins: The first really effective flea medications were found in the chrysanthemum plant: pyrethrins. And while they work well, they also have the risk of causing seizures in dogs and cats (cats are MUCH more sensitive to this medication). Many of the over-the-counter flea medications and ear mite medications will be based on pyrethrins. Look at the active ingredient. You will see pyrethrin, pyrethroid, permethrin, flumethrin or some other such variation (all of the "pyre"s and the "-thrin"s). I'd recommend avoiding them all if you can since the seizures they may cause are hard to treat and cost a whole lot more than the newer over the counter medications.

Fipronil 9.8% + (S)-methoprene 11.8% (brand name Frontline Plus for Cats): Fipronil causes seizures in the fleas until they die. (S)-methoprene prevents baby fleas from hatching out of their egg. No hatching = no new adult fleas (but you would still need to wait for the existing adults to die of old age without the Fipronil part).

Fipronil 9.8% , (S)-methoprene 8.8% (brand name Frontline Plus for Dogs): the only thing to know here is to get the right dose (by weight) for the right species. Don't give a cat the dose for an 89 to 132 pound dog and don't give a cat dose to a Great Dane. The first may cause death and the second won't do much.

Imidacloprid 9.1%, Pyriproxyfen 0.46% (brand name Advantage II for Cats and Advantage II for Dogs): just make sure you don't use the dog stuff on a cat and match your dog's weight to what it says on the box and you'll be fine.

Imidacloprid 8.80%, Permethrin 44.00%, Pyriproxyfen 0.44% (brand name Advantix for Dogs): definitely don't use this one on your cat because of the permethrins. If you get the right dosage, you're unlikely to cause a seizure in your dog (unless they are the lucky winner of an MDR1 gene mutation that lets medications get into the brain where they don't belong). Imidacloprid is going to cause seizures in the fleas. Permethrins make it so the fleas can't breath (no breathing = death). And pyripoxyfen is essentially flea birth control. The argument for using this one (even though it has permethrin in it) is for the ticks. Ticks are nasty little critters that carry all sorts of diseases.

Nitenpyram (brand name Capstar): when you need a quick ridding of adult fleas, this is your medication. Give the labeled dose (it's on the box) and the fleas will start dropping dead within the hour. The other nice thing about Nitenpyram, it can be given to really young, really small dogs and cats. The labeling says a 2 pound dog or cat that is 4 weeks old can get an 11.4mg tablet. Pro tip: these can also be given rectally (up the butt) when the animal won't swallow it. But please, use some lube (KY will do) and wash your hands after. Nitenpyram doesn't keep working so you're still going to need something long-term (one of the above will do).

A note on flea collars: While flea collars are popular, it seems that most of them only work well if the dog stays perfectly still. When the dog moves, the flea killing power of the collar is where the dog was and not where the dog is. The active ingredients also include flumehtrin (one of those "thrin"s mentioned earlier that can cause seizures in some dogs and many cats.

A note on diatomaceous earth and other hippy stuff: while it has been shown to kill about half the fleas, the other half are still laying 50 eggs a day. In other words, you're not fighting a winning battle with this "natural" stuff. As far as "natural" is concerned, botulism and herpes are completely natural. Neither are very much fun. Let go of the "natural" and use something that works.

What's the Textbook approach?

That's easy: keep all the dogs and cats in your house on a flea preventative for their species (dog or cat) and weight (it's listed on the box) and use it as directed. If you already have a flea infested menagerie (and home), use Frontline or Advantage (or their generic alternatives) every 3 weeks instead of every 4 weeks for 2 months. The effectiveness of these products really drops off after week 3 and if you want to break the flea lifecycle, really going after the darn things is important. You can jumpstart the whole process with nitenpyram (Capstar) if you'd like but I'd skip the flea bombs and carpet powders and stuff.

NOTE: you're still going to see some fleas for a while because of all the flea cocoons that are hatching. Not to fear! As soon as they get on your pet and settle in for a meal, they're goners before they can start the whole flea circle of life thing all over again.

If you see some of those grains of rice stuck to your dog or cat's butt after noticing fleas, the text book says to get a stool (poop) analysis. If tapeworm eggs are seen, praziquantel is the medication you will need. Just follow the directions on the box. Pyrantel (pinworm treatment for kids) and fenbendazole (the goat dewormer) aren't going to do the trick here.

A final note: some pets get a skin reaction with some medications. If this is the case, try a different medication. If that still isn't working, start exploring some of the newer (although more expensive) alternatives for the sensitive pets in the house through a veterinarian.

What would I do if it were my dog or cat?

Honestly? Right now, we have two indoor cats and some fish. Working 12 to 14 hour shifts isn't really fair to dogs. We treat the cats with flea preventatives in the warmer months when they go on leash walks with us (yes, you read that right... check out our cat on the Vegas strip). We skip it in the winter months.

Our cat walking the Las Vegas Strip.

If we did have a flea problem, we'd do the cheapest frontline or advantage or generic we could find every 3 weeks for 2 months and then monthly until there wasn't a problem and the weather was cold again. We'd probably jump start things with a Capstar as well.

What's in my first aid kit (that I got at the store)?

Flea comb: I run in through the fur on the top of the body near the tail. If I get live fleas or lots of little black grains of stuff (flea poop, aka flea dirt), I know there are fleas there.

A topical flea preventative: Frontline Plus, Advantage II, or one of the generic alternatives as listed above. If there is a flea problem, I'll use it every 3 weeks for 2 months and then monthly to keep any new fleas from setting up camp on my pets.

Nitenpyram: to kill all the adult fleas fast.

Praziquantel: while tapeworms may be good for the waistline, they're not so good for health.

Oatmeal shampoo: This can be used if the pet is really itchy and can sooth the skin. I make sure they are good and dry after.

I avoid the topical hydrocortisones (and other topical anti-itch treatments like it) because dogs and cats will just lick it off and that may cause other problems.

What to expect after treatment (and how to prevent it again)?

You'll still see some fleas for a month or two after a flea infestation because baby flea cocoons are hatching and the adult fleas are jumping onto your pet. Fortunately, the flea preventatives will kill the fleas before they lay more eggs. And if they do lay more eggs, some flea preventatives will prevent them from hatching.

Your pet's skin will start healing up if it's inflamed (but antibiotics are sometimes needed - see a vet for that). The fur should start looking healthier and more full (but not always). And if the ear infections are related to a flea allergy, your pet should haver less of them or none at all.

To prevent a new flea infestation of your home and tapeworms in your pet, just keep them on a flea preventative year round per the instructions on whatever product you chose. But this does have to be done for all the pets and not just the allergic ones to work!


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