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Topical and oral flea control treatments are most effective

Fleas are more than an annoyance -- they can affect the health of their host dog or cat. Their saliva may trigger allergies, and the itching and scratching that ensue can lead to a more serious skin infection. Infected fleas can also transmit tapeworms and bacteria -- including bacteria that are harmful to humans. A large enough number of fleas can even cause life-threatening blood loss.

Unfortunately, fleas are not a problem that will go away on its own. In fact, ignoring a few fleas can quickly lead to an infestation. Female fleas can lay up to 50 eggs a day, many of which fall off and land in carpets, bedding and furniture. Once the larvae hatch, they remain inactive in cocoons for weeks or even months. Unsuspecting pet owners may think the problem is resolved after killing the adult fleas, but the life cycle will repeat weeks later unless eggs and larvae are prevented from maturing into adult fleas.

Experts say the only truly effective way to keep fleas off a dog or cat is with a topical or oral medication. Flea collars are generally described as ineffective and often toxic as well. Flea shampoos provide only immediate relief by killing adult fleas on the pet; they don't leave enough residue behind to kill new fleas as they hatch. As for flea dips, bombs, powders and sprays, many of them contain chemicals called pyrethroids, such as permethrin. Experts warn that these chemicals are highly toxic, especially to cats. Vets consistently say that any product containing permethrin is unsafe for use on cats, and some warn against the use of other pyrethroids as well.

Topical treatments, also known as spot-on products, are squeezed out of a tube and applied to the pet's neck or back. One advantage of these products is that they generally contain insect growth regulators (IGRs), which prevent eggs from hatching and larvae from maturing into adult fleas. This means that a single application can completely eliminate fleas for up to a month. However, these products have drawbacks as well. Although they're generally quite safe for pets, they can irritate the skin or eyes of humans, so they need to be applied very carefully, and should you come in contact with the product, it must be rinsed off promptly. Once applied, the product may take several hours to dry. During this time, it may rinse off in water, and the residue may transfer to other pets, furniture or humans. Moreover, some pet owners find the smell or feel of the spot-on treatments unpleasant.

Other flea treatments come in tablet form. These pose no risk to humans, and they don't leave any messy residue. Oral flea treatments tend to kill adult fleas very quickly, but most of them don't contain an IGR to deal with the eggs and larvae. This means that pet owners must either combine the tablet with a second treatment that contains an IGR, such as a spot-on product, or keep repeating the dose until no new fleas are hatching. Another problem is getting a pet to take the pill. While some users say their pets will gobble them happily if they're tucked inside a treat, others -- especially cat owners -- find it very difficult to get them down their pets' throats. Also, some oral medications are available only with a prescription from a vet.

Choosing between a spot-on treatment and an oral medicine is largely a matter of personal preference. Regardless of which you choose, however, you will want a treatment that's effective, safe for your pet and easy to administer. We consulted reviews from vets, pet experts and pet owners to identify products for both dogs and cats that meet all these requirements.

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