What to do when pet’s flea medication stops working

 To eliminate a flea infestation, it takes patience treating your pet and your environment.

All too often, a pet owner will come in and share their experience in which he or she regularly applies topical flea prevention, yet is frustrated that after several treatments they are still seeing fleas. There are several plausible explanations for persistent flea infestations which may have nothing to do with lack of efficacy of these products.

Apply flea medication properly for maximum effectiveness

First, I ensure the pet owner is correctly applying the flea medication to his or her pet. It is important to completely part the hair and apply the product directly to the skin so that proper skin and hair follicle distribution can occur. This is something that can be somewhat of a challenge for thick haired pets; however, the pet medication will not work properly if only the hair follicles receive the medication – it must be applied to the skin. Next, it’s important to properly follow product label directions, which may vary depending on the size of your pet. For instance, for large dogs, Advantage II requires the product to be applied on multiple spots down the pet’s back.

While it is tempting to try and save money by using only portions of products labeled for larger pets on smaller animals, it’s a process such as this that can lead to product inefficiency.

Ensure your home and yard are treated 

Another reason for products not working is by not treating your home and yard, where in some cases 80% of the flea life cycle may occur. Read how to control fleas indoors and outdoors.

In cases of heavy flea infestations, some home products such as Advantage Carpet and Upholstery Spray kills fleas and ticks quickly and continues to kill fleas for two weeks. In spite of recent discussion in the veterinary literature, the development of widespread flea resistance is still not believed to be a major factor to clients still finding fleas on their pets.

Consider switching to oral flea medications

The newer oral flea medications are becoming very popular and with good reason — they’re even more effective than topical treatments at killing adult fleas and keeping your pet flea-free. Plus, with an oral flea treatment, you eliminate the mess of topical flea treatments and the worry about whether you’ve applied the product properly.

Have you been battling a flea infestation in your home? What are some of the ways in which you have been trying to get rid of them? 

Have pet health questions? For any medical concerns, we always recommend you consult your veterinarian. However, for non-emergency questions, you can contact Dr. Dym directly using our Ask the Vet form.

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  1. Thank you Bob. All excellent points and advice.

  2. Great suggestions as well Tom

  3. Vectra worked great for 3 weeks instead of 4. I want to treat again but is it too soon?

  4. I usually have no problem using flea meds like this off label a bit early. However make sure you are treating home where much of flea life cycle occurs with products like Knock out from 1800petmeds.

  5. I have a question/problem. Both of my cats have fleas. I have treated them for the last 2 months. One month we used advantage, and the next Frontline. I have noticed they still have them, and now if i touch their back near where their tails are they both act really weird/crazy like bite me or them selves. My one larger cat has been licking/biting the fur of of both of his front legs. Has anyone else had any adverse affects like this from these medications. I am getting concerned about them.

  6. It could be a rare reaction to the flea topicals but more likely your cats still have fleas, which are making them exquisitely sensitive to touching near their tail base area, which is the most common area affected by flea bite dermatitis in dogs and cats. There can sometimes be what is called a neurodermatitis over the spine in cats with sensitive allergies, so that may be what you are seeing; known as feline hyperesthesia syndrome, which you can google in cats. I would recommend seeing your local vet for exam, as well as may need prescription flea control medication, such as oral comfortis from 1800petmeds. Also should consider treating environment inside home, as much of flea life cycle occurs in home.

  7. I can’t believe i found this wonderful site and people going through what I am going through. When I told my sister i was still vacuuming and spraying the house and treating the cat she said i was crazy and it was all in my mind. I have learned to shut up because everyone things i have gone mad. Last year, just around this time..the actual date I will never forget was December 14, 2016 when i awoken to bites on my body (and i had just had a heart attack) and then i got my cat and picked her up and there were thousands of fleas running across her stomach.. I ran her to the bathroom and grabbed dawn soap (I didnT’t know that was good but apparently it was)..This was on a Saturday. My son’s dog had been battling fleas and he had brought his dog to my house on numerous occasions and even one time showed me fleas on his dog. So i guess this was when they found a home in my house and got on my cat. nevertheless, i found live fleas running all over the bathroom; especially along the bottom of the toilet where the contractor had decided it didn’t look nice to caulk.. my son’s dog would take a shower with him, so i assume they found refuge in my bathroom. My son to this day declines to take responsibility for putting me and my cat at such a risk. So, they procreated in there and behind the new cabinet in my bathroom.. Anyway, i did the recommended protocol and went to the vet, (he wouldnt even look at my cat)…and recommended the seresto collar and I called an exterminator. Needless to say, the exterminator had very little experience in this situation and gave me very poor advise, did not tell me not to mop or any instructions.. The situation became so intense, i was bitten to death daily.. I also work from home so I have developed a severe flea allergy dermatitis as does my kitty cat. Anyway, I found another exterminator in March and have had the house done many times. I also found a wonderful site called do your own pest control who have professional exterminators help you do it yourself. I had to find another vet because i was at my wits end. The new vet said that Seresto collar had not been proven yet and took her off it and put her on Revolution and capstar. He should have told me not to remove the seresto collar for a few days bedause when i got home in March 2016..and took the collar off and put the revolution on..the fleas went crazy.. they were biting me. These fleas are so strong that they were able to jump over the shower and bite me while i showered. Anyway, it’s a year now and my real problem comes that I am going away and leaving the cat with a sitter. My vet said to dose er with revolution every 3 weeks and capstar. But the fleas are still around. I think they are at their last leg because i continue closely to monitor my cat to see if she has even a sign of a fleas,vacuum and dry swiff my floors to see what is still on them. I do not have any carpets, just wood floors, tile and moldings. But to be safe, and to ensure a cycle doesn’t begin or if I see any sign of flea dirt, I give a capstar. So, i plan to get the exterminator one more time in early December before I go away so they are not partied when i am gone. My question is, why do i still have fleas for so long with the cat on Revolution and the exterminator changing chemicals all the time. I do not have rugs, only wood floors and tiles, but….the contractor had put the floors down with about a 1/2 to1/4 space in the moldings and i think they have laid eggs there. They are also in my kitchen.. I haven’t cooked in a year because i have gotten bitten. The fleas have bitten my back while i work so all it takes is to be near a flea or flea matter and i am on fire. Anyway, do you think I should try something more drastic like changing from Revolution. I heard there is a topical form of comfortis, cheristin which i was wondering if I should try. My vet is wonderful and sells nothing else. The other Vet has something called Vectra for cats.. not sure if i should change it up now before I go away. She is due for her Revolution this Tuesday, so wondering if I should switch it up now? Try Vectra …I don’t go back to the vet who put her on Revolution because i called the office and the receptionist said they do not prescribe anything but revolutoin..So, the other Vet would sell me the Vectra. I need this vacation, but want my sitter to have no bites and the cat to stay flea free while i am away… Don’t want to cancel my vacation. I need it. Any advise.. I am trying so hard.. and have suffered so much.. and my poor cat has been so good through all this. I love her so much and want her to have a healthy life and don’t want her to be flea infested while i am away..

  8. If your vet feels it is appropriate, then cheristin is certainly a good product to try. Sorry to hear you have had so much trouble with the intense flea situation in your home. I did not find that vectra works as well as some of the others in my experience and opinion. Revolution is excellent as a preventative, but when you are over run like this it is best to use an additional product such as comfortis, etc.

  9. A few years ago I had a nasty flea infestation and tried using Frontline for a couple months with no results. I was still finding fleas on the dogs, and one of them was so miserable as he had FAD. I had vacuumed, mopped, laundered, etc. repeatedly. The majority of my floors are laminate or wood. I was completely beside myself, so I took some of the fleas to an entomologist. They were identified as Ctenocephalides canis which I was told is not a typical flea you find in northern states (Minnesota). I was told the more common flea, Ctenocephalides felis, is the one most people are dealing with when their dog has fleas (ironic, since it’s the “cat” flea!). My vet tech called Frontline and it turns out the product (at least at that time) was not labeled for Ctenocephalides canis. I put them all on Advantage and the problem rapidly disappeared. I called Frontline and they were really great about refunding me for the product I had purchased. I’m not advocating for one product or the other – just found it interesting that the type of flea can matter in terms of how it is treated.

  10. Thank you for sharing this information. I was not familiar with the fact that advantage was more effective against the dog flea over the cat flea. Most of the flea infestations in this country, even in dogs, are actually due to the cat flea. Thank you

  11. I am sick to death of fleas and so is my dog..cat and vet. They are an utter nightmare. I have just ordered some advantage to try and looking forward to spraying and vacuuming the house again.

  12. Advantage is fine to try, however you may want to try a few of the newer oral flea tablets that are available, such as prescription comfortis. Also have your exterminator treat the home with best products, as much of flea life cycle occurs in home.

  13. Have tried a lot of stuff like others. Comfortis seems to work good but my cats can smell it and even hiding it in a pill pocket is hard because they smell it there too. One cat won’t take treats and pill pushing is not fun with him. Sometimes they end up vomiting it up. The fleas seem to be building up immunity to a lot of products I used before. Going to vet tomorrow and ask for options on new products.

  14. Prescription cheritan for cats or prescription revolution from 1800petmeds. Wait to see what your vet has to say on this

  15. I tried Revolution (started 2nd dosing this week after the first dose on 12.16.16), washed everything in hot water, washed all the cats in Dawn 1 week after initial Revolution treatment and sprinkled and swept Borax into the carpet, along the baseboards and into the mattress and furniture. I’m at my wits end as I just pulled at least 20 fleas off one of my cats. The strange thing is I took the cat to the vet and they didn’t find fleas on her. The vet thought it was a food allergy. My next attempt is diatomaceous earth. Has anyone tried this? It’s food grade and can be rubbed into the fur as it is safe to eat. I plan on retreating the house with it. Any other suggestions?

  16. Food grade diatomaceous earth is fine to try, but as with other natural treatments, this is effective, but will require followup treatment of pet chronically as does not have long residual effect on the pet. You can use it in food and/or topically. To learn more about natural flea control measures, see the natural flea control sections in the books Dr PItcairn’s Guide To Natural Health For Dogs and Cats by Richard Pitcairn, DVM, phd as well as The Natural Cat by Anitra Frazier, but you could also ask your vet for script for stronger flea medication like oral comfortis from 1800petmeds for all animals in house. I find that if there is active flea infestation in the home, that you need this additional protection of oral products like comfortis during periods of heavy flea exposure. You also may want to have the home treated professionally by an exterminator in your area,

  17. nce you see fleas on your pet, it’s going to be more difficult to get them off than if you were using the medicine as protection before the pests showed up. Many vets encourage owners to use flea medication year round, but if you want, you can also begin treatment a few months before the peak flea season beings. Find out when that peak season is for you by using our Flea & Tick map, which is based off of historical weather data for your region.

  18. Dry and unhealthy skin can affect how well spot on treatments work. A good washing and combing of your pet’s coat could help with the application of the medicine and help let it do what it’s supposed to do: keep your pet happy and healthy!

  19. The first thing to check (and double-check and triple-check) are the directions of whatever flea medicine you bought. For instance, if you are giving your pet an oral flea pill like Comfortis or Capstar Flea Killer, make sure you know how often you need to administer the dosage. Or, if you are using a spot on solution like K9 Advantix, make sure you are getting the applicator under your pet’s hair and onto the skin. This is a common mistake that can lessen the effectiveness of your pet’s pest protection.

  20. I bring in rescue mama cats and kittens for foster so fleas are a recurring problem here. We try not to use to much chemical stuff in general so we use a multi approach to keeping it under control. I keep flea traps in the cat rooms, I vacuum every other day, sprinkling the carpets lightly the night before rotating between baking soda, salt (dries up eggs) and food grade diatomaceous earth / DE (lightly – lightly because it will kill a vacuum motor quickly!), I dust coats lightly with the DE, bathe them with dish soap (some people say Dawn, but I think any kind will work) if they are big enough and healthy enough), change and wash bedding often in hot water with vinegar in the wash and rinse, feed brewers yeast, and flea comb them. On bad years like this one in the midwest a treatment or something for one month is often necessary but otherwise the cheap approach and a some extra effort usually does the trick.

  21. Topical treatments revolutionized flea control when they were introduced in the 1990s. Most of the treatments are applied to the skin between an animal’s shoulder blades. The chemical is absorbed into the sebaceous glands across the animal’s skin but does not get into the bloodstream. The treatments do not repel fleas, but those crawling on an animal will absorb the chemical and eventually die, usually within four hours.

  22. Dog health care requires flea and tick prevention, deworming treatments, eye care, aural disinfectants, joint supplements, wound repair products and nutritional support. we have a wide range of dog supplies including flea and tick treatments, heartwormers, nutritional supplements, eye and ear care products like Bayer, Pfizer, Merial, Novartis

  23. A high quality flea comb provides a non­toxic way to detach fleas from your pet’s fur. These tick remover products are perfect for kittens and puppies because they do not pose any threat to sensitive skin and coat. Flea combs for cats and dogs not only help combat an existing infestation but are also great for identifying the first signs of fleas and ticks.

  24. Excellent points . Thank you for your contribution.

  25. Purchase FOOD GRADE DE powder and a duster. When any bug/flea/spider/etc comes in contact with it , it eats into their exoskeleton and kills them. Completely organic, not a pesticide. It also fills larva. Any bug in any stage. Recently moved into a house that was occupied f by two incare3d for dogs. I dusted my entire house. Under fridge, under and behind stove, all along baseboards, inside cabinets (does not matter if it gets onto your plates, etc as it is non toxic/organic and can be eaten_i, as well as both my pets consume it) I have dusted every portion of this house and after one month_no more fleas. NADA. So it may appear awkward as you will have white powder all over your floors but it is certainly better than fleas. I must also warn yu that every flea bit brings with it parasite such as tape worm. I also feed my dog/cat this every day for 30 days to rid and break cycles of any hook, whip, etc worm they may come in contact with. You can also dust your pet with this. I still use comfortis for my dog at half doses but my house is dusted. My indoor cat has yet to have a flea on her due to my dusting

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