For pet owners who find topical treatments messy or inconvenient, medications in tablet form can be a simpler solution to a flea problem. Capstar for Dogs and Cats (Est. $30 for six doses) is an over-the-counter medication that works on both cats and dogs between two and 25 pounds in weight. Capstar for Dogs (Est. $25 for six doses) is the same product but in a higher dosage and is intended for dogs over 25 pounds.
The active ingredient in Capstar, nitenpyram, works very quickly, killing adult fleas in as little as 30 minutes. This means Capstar can provide quick relief for pets with flea allergies. What it can't do, however, is kill flea eggs and larvae. But Capstar can safely be given as often as once per day, so pet owners have the option of repeating the dose if their pets are re-infested.
Since Capstar is a pill, it poses virtually no risk to humans who use it. Side effects in pets are also very rare. In more than 1,000 owner-written reviews across sites such as Amazon.com and 1800PetMeds.com, we found only a handful that mention any problems at all and none that describe serious reactions. Capstar is also effective in most instances; many say they were "shocked" to see how quickly the fleas fell off their pets. That said, some reviews complain that the product didn't work for their animal or that its effects only lasted a couple of days. Another problem some users have is getting their pets to take the pill. According to reviews, dogs will usually take the pill if it's tucked into a treat like peanut butter or cheese, but cats may be more reluctant to swallow it.
We also saw many positive reviews for an oral medication called Comfortis (Est. $90 and up for six doses). Like Capstar, Comfortis works only on adult fleas, but its effects last a full month, so vets say it will continue to kill new fleas as they develop. Unlike Capstar, Comfortis is available only with a prescription from a vet, and it can only be given to pets at least 14 weeks old.
Veterinarians tend to be enthusiastic about this treatment. The vets at Twin Maples Veterinary Hospital in West Carrollton, Ohio, praise its ease of use, while vet Eric Barchas, writing for Dogster.com, says it's a great choice for dogs who are prone to skin problems. Owners generally find Comfortis very effective as well, with many saying it worked on their pets after other products had failed. At 1800PetMeds.com it earns a 4.5-star rating following more than 1,000 reviews.
However, it's also much more likely to cause negative side effects than Capstar. Vomiting is the most common problem, and Barchas admits that "a small proportion" of dogs will be unable to use Comfortis for this reason. The reviews we consulted from users included rare reports of more serious side effects as well. Dogs are more likely to develop those side effects than cats. Comfortis must be administered exactly as directed, and it can also interact badly with certain other medications, including ivermectin, which is used in most treatments for heartworm. The manufacturer advises pet owners to use this product only under the guidance and supervision of a veterinarian.
Most pet owners find Comfortis easy to use. Users like the fact that, unlike topical treatments, it doesn't have any odor or leave a greasy residue on the pet's fur. However, a few pet owners say getting the pet to take the pill can be tricky. Some users say their pets ate the beef-flavored tablet right out of their (the owners') hands, but others say they had to resort to tricks like slipping it in a "pill pocket" or grinding it up and mixing it with peanut butter.
Elsewhere in this report:
Best Reviewed Flea Control Treatments: Whether you -- and your pet -- prefer a spot-on treatment or a pill, these are the flea control products that experts and users say kill fleas dead. All are effective, and safe.
Best Flea Treatments: Spot-on flea-control treatments are applied to the skin. Reviews say they are the most effective way to rid your pets of their pests, and these are the top choices.
Buying Guide: Finding a flea treatment that keeps you and your pet safe, but kills fleas fast and effectively, can be a challenge. These is what you need to know to find the best choice.
Our Sources: Where can you find the best reviews of flea treatments? Our editors used these reviews and guidance from veterinarians, pet experts, scientists and everyday pet owners in compiling this report.