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Why are my cat's flea drops not working? How to eliminate fleas?

Updated On September 23rd, 2025

I have been using the prescription revolution flea drops from my vet for my cats since they were 2 months old, now almost 11 months and they still have many many fleas. Is their another solution that can get rid of these fleas??

3 Answers

Most Helpful Answer

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Answered By Rodrigo Roca, DVM

Veterinarian

Published on May 22nd, 2018

SIGNS OF TOXICITY All flea control products are potentially toxic or may produce unexpected side effects. Toxicity may result from accidental overdose or unexpected sensitivity. Known side effects, although rare, are vomiting, diarrhea, drooling, sluggishness, weakness, or abnormal behavior. If you suspect that your animal is reacting adversely to a flea control product, stop using the product and consult your veterinarian immediately. If the reaction occurs immediately after application, the product should be rinsed off thoroughly and the animal brought to the veterinarian for evaluation. Adverse reactions may occur from minutes to days following application. Insecticides can be toxic to people; all products should be handled carefully, avoiding direct contact as much as possible. Keep all products out of the reach of children. Cats are particularly sensitive to many pesticides. ONLY USE PRODUCTS LABELED TO BE SAFELY USED ON CATS. If you have any questions about a product’s safety, please consult your veterinarian. FLEA CONTROL IN YOUR ENVIRONMENT Immature life stages of the flea accumulate in the environment when animals with fleas serve to disperse flea eggs into the environment where they then hatch into juvenile life stages. House and yard treatments need to be concentrated on "source points", which are areas where your pets spend most of their time. This typically would include the bedding and resting areas, the feeding location, etc. You can lessen the flea burden in your home by thorough vacuuming of all source points followed by disposal of the vacuum bag and by washing all animal bedding weekly in hot water and drying at high heat for twenty minutes. Steam cleaning of rugs and carpeting +/- upholstery is also helpful. In the yard, focus on areas where your pet(s) or other animals spend most of their time. Typically, fleas survive and reproduce in shaded, moist areas with plant or organic debris (under decks, bushes, storage sheds, etc). Fleas do not survive or reproduce well in sunny, open areas of lawn or patio. Elimination of yard debris will be helpful in reducing flea numbers. You may choose to utilize a professional exterminator service for the treatment of fleas in your home and garden. REALISTIC EXPECTATIONS It is important to realize that the various anti-flea medications do not eliminate the immature forms of fleas in the environment. Thus, for the first month or so you may continue to see fleas on your pet as the juvenile forms mature and search for a new host. This does not mean that the fleas have built up resistance to the medication – in reality, flea resistance to these products is quite rare. The most common reasons for failure to control a flea problem are: 1. Frequent washing of a pet treated with a spot-on product (this includes swimming in pools, lakes or the ocean). 2. Inconsistency in the application of the product. 3. Failure to treat all pets. 4. Wildlife reservoirs of fleas (feral cats, raccoons, opossums, coyotes, etc.). Thus areas below outside decks, old sheds, etc. should be barricaded or locked to discourage such ‘visitors’.

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Other Answers

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    Answered By Rodrigo Roca, DVM

    Veterinarian

    Published on

    Hello, sorry to hear about your flea problem. It is truly a much more complicated problem than it seems and it often involves treatment of your entire environment in order to rid the fleas. You often also need rapid kill medications intermittently to kill adult fleas rapidly. Here are some tips on how to manage severe flea infestations at home. Hope this helps and best of luck. The adult flea spends most of its time living on cats and dogs. Fleas lay eggs on the animals, but these eggs rapidly fall off the pets and are distributed in the parts of the environment where the pets spend most of their time. The eggs hatch into larvae which evolve into pupae (cocoons) emerging in the future as adult fleas. For one adult flea found on your pet there are at least one hundred immature fleas in the animal's environment. Flea allergy is the most common cause of itching and scratching in the dog and cat. When the flea bites your pet, it injects a small amount of saliva into the skin. Dogs and cats can develop an allergy to this saliva and will react to it with severe itching and scratching. This itching sensation may last for up to two weeks after the last flea bites. In the dog, the most commonly observed signs of flea allergy are biting and scratching around the rump, tailbase, and groin area; "hot spots;" and secondary skin infections. Cats may manifest flea bite allergy more subtly. You may see areas of hair loss and scratching, but more often you will feel small scabs and bumps around their neck and down their backs (commonly known as miliary dermatitis). It may seem confusing to you to be told that your dog or cat has flea allergy dermatitis if you never see fleas. This is mainly due to the fact that your pet has a remarkable capacity to either scratch, lick or chew the fleas off. In addition, the more allergic the pet is to the flea’s saliva, the less fleas are necessary to make the pet itchy. You may also find evidence of fleas on your pet by using a fine comb and brushing out the "flea dirt" that they leave behind. This "dirt" looks like small black dots, and is the excrement of the flea. When placed on wet paper, it dissolves in red streaks because it contains partially digested blood. The only long term efficacious and safe therapy for flea allergy dermatitis is to keep your pet from being bitten by fleas. Remember, successful resolution of the flea allergic animal's misery requires that the fewest possible number of fleas bite your pet. RECOMMENDATIONS FOR FLEA CONTROL The control of fleas is an ongoing process, but once initiated, it is not difficult to sustain. The following recommendations will assist you in this control, but you should remember that they are simply guidelines to follow. The flea control program you use must be tailored to you and your pets individual situation. Just as we are constantly updating our protocol, it is necessary for you to change yours as new products become available and the efficacy of those now in use are altered by time of year, location, and reformulation.

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    Answered By Rodrigo Roca, DVM

    Veterinarian

    Published on

    Cats: If you own cats, they must be involved in the flea control program even if they are not exhibiting any problems, or they will carry the fleas to your house, yard, and dogs. Cats are more sensitive to the chemicals in flea preparations, and many insecticides can not be used on them. For cats, we recommend using either Revolution® (selamectin), Frontline Plus® (fipronil and methoprene), Advantage® (imidacloprid), Advantage Multi® (imidacloprid and moxidectin) or Cheristin™ (spinetoram) in the feline formulation. Another product is Vectra™ (dinotefuran and pyriproxyfen) for cats. All these products are applied in a similar fashion as in dogs. Beginning at the base of the head, part the hair and apply the small amount of liquid to the skin (not the haircoat) along the back of the neck. Application also varies from two to four week intervals, depending on other treatments. Please follow the instructions outlined for your pet. Capstar® (nitenpyram) is also safe for use in cats as a “quick kill” in the event fleas are seen, or can be given every one to three days for routine flea control if an oral product is desirable. Comfortis™ as a monthly oral tablet is also safe to use in cats. Juvenile Flea Stages: There are several life stages that occur before a flea becomes a biting adult. Some of these juvenile stages are also targets for flea control. Decreasing the numbers of immature (juvenile) fleas can be an excellent way to help prevent adult fleas and thus flea bites. Research has led to the release of several products that interrupt the life cycle of the flea. Often these products are used in combination to quickly and effectively decrease the flea burden of your pet. Synthetic juvenile flea growth hormone imitators are found in many flea products. Methoprene (Precor®) is contained in Frontline Plus® and Certifect™ as well as many of the indoor area treatments. Vectra 3D™ contains pyriproxyfen as one of its active ingredients. All of these synthetic hormones are very safe to use on animals and around humans. They prevent the adult female flea from laying viable eggs and prevent immature fleas from developing into adults. Program® (Lufenuron) is an oral chewable tablet available for both dogs and cats that is given monthly with food. As the adult female flea feeds on the dog or cat, the female flea lays eggs that cannot hatch and larvae that will not survive. This product is very safe, but flea-allergic animals also need protection from the biting adults. Program® is best used in combination with a topical or oral flea adulticide. Another formulation available is lufenuron in combination with milbemycin, a monthly heartworm preventative. This product, called Sentinel® is also given monthly with a full meal. Most other forms of flea control on your pet have been scientifically shown to be ineffective. Flea shampoos will only kill the adult fleas but have virtually no residual effect, and will not prevent reinfestation once they are rinsed off. Electronic flea collars, brewer's yeast, garlic, vitamin B tablets, and extracts of eucalyptus or pennyroyal, are not flea repellent, and provide no protection for your pet. Lastly, flea combs, although helpful, are similar in effect to the use of flea shampoos alone; they do not prevent reinfestation.

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