Image from the CDC.gov
The average pet owner is aware that fleas are a pesky parasite that feeds off of the blood of our pets. They know it causes itching, and that fleas bite us too. They can live in our carpets and sofas, and prove to be quite hard to kill once they've made their way into our homes. We know there are topical preventatives we can give our animals monthly to prevent fleas, and those topicals also usually prevent one or many other parasites like worms and ticks.
Fleas are found world wide, and can live on any species of animal, though they have some they seem to love more. People hailing from southern or any warmer region know they are a constant threat. Fleas are laid onto the host, or your bedding, etc. and then fall off and can scatter to other places and animals. Before reaching adulthood, they can remain 'babies' for up to 50 weeks! That's about a year; the pupal phase of fleas can sit around and just wait. They wait until there is some kind of movement or warmth stimulation, ie. you or your dog picking them up. So while your topical could have killed the adults, the eggs could have burrowed into your carpet.. waiting almost a year, to be picked up again where they will hatch.
Severe infestations can cause your pet to become anemic, while others can develop a flea bite hypersensitivity. This sensitivity is caused by their saliva, and they don't need to be infected with many fleas to get this condition. They will scratch and possibly develop pustules or hot spots.
Fleas are carriers of several awful things. We know they can spread Bubonic Plague or endemic Typhus to humans. They are also the intermediate host for the "flea tapeworm" we see in our pet's feces. Our pets ingest the fleas during grooming, where they grow and we see evidence of the infestation in the either long, or "cucumber seed" looking segments in their stool. They are somewhat flat, and can look long and worm-like, or the smaller segments can break up as they exit and look like seeds. While rare, our human children can also contract this tapeworm by ingesting infected feces or fleas. We grown ups tend to know to stay clear!
Naturally we can see fleas with the naked eye most of the time. When in doubt, you can use scotch tape against your pet's skin to try to pick up either the fleas or their "dirt", which looks like bits of dark sand pellets. This is actually *their* feces, and it's your pet's blood. If you pull off this dirt, you can put a few crumbles onto a paper towel and wet it. If it dissolves into a red color, you know it's blood from the feces of the fleas. To determine if your pet has flea allergies, your vet can make that diagnosis.
Prevention is the best medicine, and even that can be hard. If your home is carpeted or you have plush furniture, it will prove very difficult to get those eggs out. A vacuum, if it doesn't leave them behind, will still leave them in the vacuum bag. Yards themselves can be infested.
There are several products out on the market to ward of fleas, ticks, and flat and/or round worms. Ask your veterinarian what they recommend. If you live in a warmer climate, don't think your pet should only be on preventative when it gets warm. Remember, those eggs live in our homes just waiting.. and our homes are warm! Monthly preventative, year round, is the only way to save yourself the horror of never feeling like you can get those things out of your house and off of your pet. We are carriers; I had indoor cats who weren't on preventative who all became infected. Clearly I brought eggs or adults into the house by another source. Luckily all my floors and furniture were wood and they managed to never reach my bed!
There is a drug found in some preventatives called Ivermectin. It's very effective, but toxic to certain dog breeds and many owners are not aware of this. We have what is called the "blood-brain barrier" in our brains, which prevents unwanted things from passing into our brain tissue while allowing other good things in. There is a defect in this barrier in Collies, Australian Shepherds, Old English Sheepdogs, Longhaired Whippets, and Shetland Sheepdogs (Saunders Handbook of Veterinary Drugs). Since it can pass the barrier, it is neurotoxic and can cause hypersalivation, depression, ataxia (uncoordinated movement/difficulty walking), difficulty with vision, coma, or death. If you believe your dog to be mixed with any of these breeds, consult your vet before choosing your preventative. If you have a very young animal or a pregnant animal, always consult your vet before doing anything, regardless of breed or species.
Fleas are naughty, naughty creatures and should not be taken lightly. I have met many people who approach medicine more naturally, and I have never heard of any natural remedy that seemed to be effective. If any reader has used something more holistic and found it effective, please let us know! We hate putting chemicals on our animals, but often it is incredibly worth it.