Topical Flea Treatments

Growing concern over adverse reactions from topical flea control treatments

Topical flea control treatments are applied directly onto a dog or cat's skin, usually between the shoulder blades or in several locations down the back for dogs, or at the base of the neck for cats. The animal's natural body oils distribute the medication throughout its skin and hair to effectively eliminate fleas within about a day. The topical treatment remains effective for about a month, even after bathing or exposure to rain (although some labels say not to bathe your pet for a few days immediately following the applications). These medications are meant to be used for short-term flea control; if your pet is susceptible to fleas and you'd like to keep him or her pest-free long-term, experts say you should look into oral flea medications. Topical flea control treatments that contain pesticides must be registered by the Environmental Protection Agency (EPA) before being marketed to consumers to ensure that they are safe. (The Food and Drug Administration is responsible for regulating oral and injected medications.)

In April 2009, the EPA announced its intention to re-evaluate spot-on pesticide products for flea and tick control due to an increase in the number of reported incidents of adverse reactions in dogs and cats. In 2008, there were 44,263 reported harmful side effects, a 53 percent increase from the previous year. Problems included skin irritation or redness, loss of appetite, vomiting, diarrhea, excessive salivation, trembling, depression, seizures and even the death of pets. In March 2010, the EPA announced it will be reviewing labels to determine which need stronger and clearer labeling statements. Additionally, the EPA says it will "develop more stringent testing and evaluation requirements for both existing and new products." Some of the changes consumers can expect to see in the foreseeable future are different brand names for dog and cat products and clearer instructions and dosage information to prevent misuse.

The Center for Public Integrity, a nonprofit that engages in investigative journalism, analyzed the adverse reactions in pets reported to the EPA over the last five years. They say at least 1,600 pet deaths are related to spot-on treatments containing pyrethroids, which is "about double the number of reported fatalities tied to similar treatments without pyrethroids, such as Frontline and Advantage." Permethrin can be lethal to cats and is one type of pyrethroid found in some topical flea treatments for dogs. Many of these incidents involve a product with permethrin intended for dogs being mistakenly applied to a cat. Bio Spot Spot On Flea & Tick Control for Dogs is 45 percent permethrin; K9 Advantix is 44 percent permethrin. More information about permethrin is available through the National Pesticide Information Center (NPIC).

Despite this backlash from consumers, many pet owners have been successfully using topical flea treatments on and off for years. Although most topical treatments are available without a prescription, experts strongly recommend consulting a vet before administering them to a dog or cat, especially pets that are young, old, sick, pregnant, nursing, taking other medications or diagnosed with a skin condition. It is extremely important that you do not use a dog product on a cat and vice versa. Additionally, the dosage of topical products varies according to the pet's weight; serious or life-threatening side effects can result from using a topical treatment that's too potent. These products also have minimum age requirements for puppies and kittens, which varies from six to eight weeks old.

Topical flea control treatments are administered once a month and are usually sold in a multi-pack of three or more doses. Topical flea control treatments contain a pesticide that kills adult fleas, but active ingredients vary in some way for each product. Some products also contain an insect growth regulator (IGR), which breaks the life cycle by preventing flea eggs from hatching and larvae from developing into adults. Additionally, some topical treatments contain chemicals that repel or kill ticks, heartworms, roundworms, mosquitoes and/or lice.

The NRDC publishes a directory of flea control products and information about their toxicity at SimpleSteps.org. This organization rates topical flea treatments at a higher risk level than oral flea medications. The group cautions against using topical treatments around young children and pregnant women.

Pet experts and owners are pretty much split between which of the two top brands -- Advantage or Frontline -- is the best topical flea treatment (neither formula contains permethrin). Veterinarian Eric Barchas at Dogster.com recommends both Advantage and Frontline, saying they "have very low rates of adverse reactions, and when adverse reactions occur they rarely are serious." The U.K.-based Feline Advisory Bureau recommends Advantage and Frontline over oral medications for treating fleas on cats. Advantage is less expensive, and we read many reports from pet owners of Frontline losing effectiveness after years of use (we didn't see this proven scientifically, however). Advantage and Frontline brand products are available online without a prescription; however, the EPA cautions that some retailers may be selling counterfeit products, so buy from a reputable dealer or pet store.

If you spot fleas on your dog or cat, Larry Cohen at DrLarryPetVet.com says Advantage is the best choice for killing them. Advantage for Dogs (*Est. $55 for a six-month supply) and Advantage for Cats (*Est. $55 for a six-month supply) contain the active ingredient imidacloprid, which kills nearly all fleas on the pet within 12 hours. It also kills flea larvae, which helps to break the life cycle and prevent a reinfestation, as well as chewing lice. It doesn't, however, prevent flea eggs from hatching or kill ticks. No prescription is required to purchase Advantage, which is sold in a package with a four-, six- or 12-month supply. It is safe to use on puppies as young as 7 weeks and kittens as young as 8 weeks.

Advantage is the top-rated product at 1800PetMeds.com following hundreds of user-written reports. Advantage for Cats is also top-rated at Amazon.com, where it again draws a thumbs-up from the majority of the hundreds of user reviewers. Owners agree that regardless of whether it's the dog or cat version, Advantage is simple to administer and that their pets quickly stopped biting and scratching fleas. Advantage for Dogs hasn't accumulated as many reviews, but pet owners so far give it mostly good grades.

Reviewers at PlacervilleVet.com, a veterinary clinic website, say that Advantage is "safe and fairly effective," but that Frontline works longer and is more effective. Additionally, if you need a product that kills ticks, the active ingredient (fipronil) kills them within 48 hours. Like Advantage, Frontline Top Spot for Dogs & Puppies (*Est. $60 for six-month supply) and Frontline Top Spot for Cats & Kittens (*Est. $60 for six-month supply) kills the majority of adult fleas in a 12-hour period. Another version of the product, Frontline Plus for Dogs (*Est. $75 for six-month supply) and Frontline Plus for Cats (*Est. $70 for six-month supply) is more expensive than Advantage and Frontline Top Spot, but it also kills flea eggs and larvae. Frontline products are safe to use on puppies and kittens at least 8 weeks old, and are available in a package with a three-, six- or 12-month supply.

Frontline Plus for Dogs is the top-rated flea control product in user reviews at Petco.com and Amazon.com. Overall, most pet owners say they are satisfied. However, a significant number also award Frontline Plus for Dogs the lowest ratings. Some say it never worked, and others say it stopped working after years of use. There aren't many complaints of an adverse reaction in dogs from this product.

Frontline Plus for Cats receives an average rating of 4 stars from about 375 users at Amazon.com but, again, reviews are mixed, with a notable minority giving it the lowest rating. Complaints about long-term effectiveness mirror those for Frontline Plus for Dogs. At 1800PetMeds.com, reviews for Frontline Plus for Dogs and Frontline Plus for Cats are grouped together. Nearly 1,500 reviews have been posted here, but the overall rating is unimpressive. Satisfied pet owners say Frontline Plus has worked well for years, but may take a month or longer to completely eliminate an existing flea problem. Disappointed pet owners say their pets still have fleas. Some say Frontline Plus worked in the past but recently stopped working. Some cat owners report fur loss at the application site, but there don't seem to be a large number of pet owners reporting serious adverse reactions.

Revolution for Dogs (*Est. $100 for six-month supply) and Revolution for Cats (*Est. $80 for six-month supply) cost more still, but control a range of parasites in addition to killing fleas and their eggs (Revolution doesn't kill larvae); in addition to fleas, Revolution controls heartworm, hookworm, roundworm, ear mites and sarcoptic mange (caused by a mite that lives in the pet's skin) and kills the American dog tick. One downside is that a prescription from a vet is required to purchase it online. Another downside is that the time frame for killing adult fleas is slightly longer -- 24 hours for dogs and 36 hours for cats.

Revolution receives a good average rating from pet owners at 1800PetMeds.com, who say it dries quicker than other topical flea treatments and keeps fleas off pets. Some pet owners say they have been using Revolution for five years or more. Some owners say their dog got fleas or heartworms on Revolution and some cat owners report adverse reactions like hair loss, wheezing, seizures and death.

Two topical flea control treatments for dogs that contain permethrin -- K9 Advantix (*Est. $80 for a six-month supply) and Bio Spot Spot On Flea & Tick Control for Dogs (*Est. $25 for a six-month supply) -- receive lower reviews from pet owners posting at 1-800-PetMeds.com, Amazon.com and Petco.com. Dissatisfied users say that those products either didn't work or that their pet had an adverse reaction, ranging from sores at the application site to seizures, vomiting and a host of other worrisome side effects.

Another topical flea treatment for dogs that contains permethrin is Vectra 3D (Est. $90 for a six-month supply). It also contains the IGR pyriproxyfen to kill fleas at all stages of development like Frontline Plus. It is the most expensive flea control treatment and requires a prescription, but also repels and kills adult mosquitoes, lice, mites and sand flies. We didn't find any pet owner reviews for Vectra 3D online, but veterinarians at PlacervilleVet.com say it works better than Frontline Plus, particularly on fleas. The manufacturer, Summit VetPharm, says Vectra 3D is safe to use on 7-week-old puppies.