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Are the combination chewable heartworm/flea/tick medications safe for my dog?

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  1. tb

    I recently switched to a natural heartworm prevention due to two of my four dogs vomiting after each monthly dose of a chewable. I live in an area of the US that has a high rate of heartworm infection. Are there any viable, natural methods of prevention you can recommend.

    1. Michelle

      Curious……What are the natural products you are using?

      1. Diane hollo

        Simparica and interceptor plus

  2. T Allen

    Thanks for writing about this! I live in a severe Lyme area and was wondering if any of these would stop the ticks from biting long enough to prevent disease transfer. From what I’ve learned about Lyme and it’s co-infections (I’ve been infected) any tick bite for even a few minutes can transmit these diseases.

    Can you give us any info the use of repellents? I want to use herbs etc but if they aren’t highly effective the risk is great. Is Picaridin any safer on animals then Deet? Is my indoor cat at risk from contact with the dog or his bedding with any repellents? Thanks!

    1. Fran Miller

      Synergy Labs produces a spray called Richard’s Organics. We have used it with much success and we live in Columbia County NY, a tick hotspot. Hubby did an experiment with live ticks and the spay once it hits the ticks they back out ASAP. Did not experiment on the dog, just on his own hands. Works very well for the dog in question who is 18 years old. It contains the following: connamon oil 1.5%, rosemary oil 1.50%, peppermint oil 1.5%, cedar oil 1.5%, clove oil 1.5%,eugenol 1.5% and the inert ingredients are: purified water, polysorbate 20, vitamin E and soduium benzoate.

      1. Korishan

        Fran: Thanks for the ingredients listing for this formula. I plan on getting the oils and mixing the batch myself (I will also look into premade version for cost comparison). But I was wondering what the ratio of oils to water was. Or, being 1.5% for the oils, is that about 90% water? And what about the Vitamin E and Sodium Benzoate?

  3. MikeN

    My girl would get severe diarrhea from Trifexis so we switched to topical Revolution. We’ve noticed zero side effects with its use and find that it protects from fleas very well.

  4. TN Resident

    My local pet supply store, Wags & Whiskers, has recommended “Wondercide”. It’s a natural product with only 3 ingredients:cedar oil, lemongrass oil, hydrated silica. It claims to kill and repel fleas, ticks, AND mosquitoes. It also has other benefits- I have only been using it for a week but am pleased so far. I decided last year I’m not giving my pet any more insecticides like the monthly heartworm and flea pills.

    1. Sherrie Ashenbremer

      Please give your dog heartworm preventative of some kind. I want your dog protected from this horrible disease

    2. Nouble

      Even though it’s great that you’re trying to avoid the synthetic chemicals, make sure they’re safe for your pet. You do not want to end up poisoning them.

  5. Ann Marie

    Both of my Golden Retrievers have had a sever reaction to Trifexis. My English golden female Maggie had to be rushed to our vets where she spent the entire day, had I not been home to see the foaming mouth and almost complete inability to stand I am not sure she would be with us today. My vet to this day will not blame the Trifexis, however that was the only thing that had been given to her and had been changed! I don’t believe one needs to be a doctor of veterinary medicine to put it together I just believe our vets need to start challenging the b.s. of the shots, drugs and foods out there and not be completely complacent with the, this is the way it’s always been done attitude.

  6. Peter

    I am happy to see an explanation of how these drugs work using plain words.

    Since these ingested insecticides are systemic, users are assuming serious risks. They work by “attaching” (my word) to (blood) plasma for distribution throughout the body. The insecticide reaches the highest concentrations in fat, followed by liver, kidney and muscle. As a metabolic process, the insecticide is “persistent” and slowly eliminated from plasma… this is how it stays concentrated for long periods between doses. The dog eliminates the insecticide primarily in his/her feces. Secondarily, the dog’s renal system works overtime to cleanse the blood and eliminate the “toxin” and this is why dogs experience adverse reaction primarily in kidney or liver failure. The list of side effects goes on and on. These products are incredibly dangerous.

  7. Debbie

    I would love to hear more about natural. I ha e used shoo oil on their collars which worked for years but with the increase in flea population it couldn’t keep up. I had to go to comfortis especially as my one developed bad sores from the bites. Really hate ingestion of chemicals but what else is there that is as effective?

  8. Joy

    I was thinking of switching from Frontline + to Nexgard. I live in an area that has high rates of tick borne disease. Not so sure after reading this. My vet and his staff swear by the Nexgard.

  9. Luvs dogs

    Yes! Please, please recommend some natural alternatives to these medications. I’m sure that there are plenty of pet owners that would love to switch to alternative heart worm, flea, and tick preventatives but we aren’t given any info so that we can do so. I’ve been using do Terra’s terrashield & applying it like Frontline along with Neem spray whenever I walk my dog. I would really like to try some other recommendations if anyone has any? I’ve already lost one dog to cancer & can’t help but think that he got it from these chemicals.

  10. Robin Sherwin

    I live in Portland Oregon. Fleas and to some degree ticks are a problem In the summer we have a lot of mosquitoes but fortunately heart worm isn’t a big problem here. I used topical products until I read how toxic they are. When they break down they are even more toxic! Finally I bought a tag for my dog to wear on her collar which emits a energy that repelled bugs. (Google it)

    I didn’t have much faith in it, but it came with a money back guarantee. I was amazed to watch the mosquitoes buzz around her but not land. I considered buying one for myself!

    You have to ensure that there are no fleas to begin with, which is easy when the temperatures are freezing and you can give your dog a flea bath first. I used it for many years with very good results, until we chose to put her down at 17 due to multiple health issues and weight loss. I was glad that we did not have to use toxins on her as she also had lymphoma.

    1. Linda

      Robin, what tag are you speaking of? Name? Thank you!

      1. Rachel

        Sonic Guard Flea & Tick pendant or Easy Defense Flea & Tick tag

    2. diva

      Name of tag please, and we’re can i get this tag.

      1. Rachel

        Sonic Guard or Easy Defense – google them to buy online

  11. Lori S.

    I am concerned with the responses asking for natural mosquito, flea and tick remedies. I think that people forget how deadly insect-borne diseases are. Heartworm and Lyme disease are epidemic in some areas and are very serious. Yes, there are risks to drugs, but there are also risks, serious ones, to avoiding drugs. I have adopted two animals who already had heartworms. The cure was grueling (and risky) for them and their lives were shortened from the disease. If you don’t want to go with newer drugs that haven’t been around long enough to be well tested, a reasonable concern, then consider using older meds, such as Frontline and Heartgard.

    I am hoping that those of us who want safe food are not becoming anti-science and anti-vaxers, as that will be dangerous to our pets, and will also lower the movement’s credibility.

    1. melly

      i disagree with you yes lot of disease are rampant but the use of chemical is not a solutions
      i personnelly do not use any chemical on my dogs and cats if i need to use any product i get the natural herbal spray on for tick and mosquito from
      the only product that i use is interceptor for heartworms and i only use it for six month
      i never had any flea on my dogs or in the house in the last 20 years
      none of those chemical company care about your animals they only do it for profit
      nothing to do with science

    2. Nouble

      I guess you’re just going to gloss over the fact that Frontline and Heartgard have caused plenty of pets to fall ill. (They don’t seem to have a place for Haertgard complaints and reviews.) Also, I feel that your last sentence gets a little off track.

  12. Dianne

    I know I have ticks in the back part of my yard, but I am loathe to cut the bushes down. I wish I could borrow a few chickens for a day. They are supposed to be good at tick removal.

  13. e d barber

    My friends and I used this homemade bug repellent for our horses. It worked well for several of the barn’s dogs too. It was 1/4 Skin so Soft (Avon), 1/4 citronella oil, 1/4 apple cider vinegar and 1/4 water. Spray it on. It kept flies and mosquitoes and ticks off the animals in the summer. None of the animals had any side effects but one owner got migraine headaches if she did the spraying.

    1. Jo

      I think I’m going to try this! I’ve been looking for something like this! Thanks! 😊

    2. Diane Ethridge

      I would check with a vet before spraying cats with anything containing
      citronella. They are very sensitive to that product and citrus in general.

  14. Nina Wolf

    Win-win. That is exactly the problem. Charge us to cause the problem, charge us again to fix the problem. The growth of the trend to see animals and family member and treat them as well as we possibly can has a downside: we get duped. We want to do the best we can, so we fall for the have heavy marketing, the tales of all the bad things that will happen if we don’t vaccinate all the time for everything, the warnings that this national brand flea and tick protection is absolutely necessary. Bias. Just remember that word: bias. When a pet food company or a professional gives you advice, ask what bias they have. Who is paying them to say this, who paid for the studies they are citing? Follow the money.

  15. Diana

    There are natural flea/tick products on I have some on order, so cannot comment on effectiveness. There are many positive reviews, tho so chk out the website to see for yourself. I am not a rep, just a pro dog trainer of 20 yrs. I never give my dogs heart worm meds as I would rather treat the issue than give meds unnecessarily. They are tested yearly for HW, with never a positive. Only vaccine given(as adults) is rabies. My dogs are fed clean diets are are happy, trained and well exercised. I have always used Frontline, but will be trying out all natural flea/tick products this year. We live in Georgia.

    1. Karen Mitchell

      Hi Diana, If you wish to learn more on PMR or BARF diets (Prey Model or the Biologically Appropriate Raw Food Diet), natural remedies, prevention and supplements, there’s my Facebook group “As Nature Intended”. If you have problems finding it, message me direct in FB. I don;t think I’m allowed to share the link

  16. Cathy Alinovi

    This is a fantastic discussion – I will followup with some suggestions for next week’s blog.
    Dr Cathy

  17. Kat Steele I recommend looking for a holistic vet in your area, to see what they recommend (that is what I plan to do this year). We have used the chewable heart worm medication for years w/o issue but I am concerned with the newer multi-purpose chewables and using the topicals. Additionally, Frontline seems to have lost its ability to keep tics off my dogs (at least that has been our experience the last 2 years) and we have a huge issue with dear tics and Lymes disease in our area…Cats are also now getting heart worm; while I have not gone down that path with our cats yet because we keep them indoors, mosquitoes do get indoors somehow (as well as ride in on the dogs fur).

    1. Sherrie Ashenbremer

      We have no Holistic vets in my area, Grand Rapids, Michigan. Had one and she retired. I wish we had one

  18. Nellie

    One of my dogs almost died from Trifexis. She was completely unresponsive the morning after she received her second monthly dose. After spending the day with the vet she was better, but had lost the use of her back legs. Fortunately with the vet’s supportive care she was better by day 2, but I’ll never give her that crap or anything like it again. I’m one of the lucky ones, I’ve read about a lot of peoples’ dogs not pulling through after taking this drug. I can’t even believe I thought it was a good idea to put them on this now that I know more about what it is and how it works… Just common sense, don’t feed your pets poison. Would you eat poison?

    1. Sherrie Ashenbremer

      That is horrible, glad she is better

    2. Nouble

      I’m so sorry that you had such a horrible experience. I’m glad that she’s better!

  19. Karen Mitchell

    To answer this articles question. NO!! Avoid these toxins like the plague!!!

  20. Nouble

    Some time last year, I stopped trusting those medicines when I noticed the EPA label on their product. Wait a minute. They handle the environment; what are they doing producing medication? (Then again, that would explain the toxins.)

    I feel that there are two medications you should avoid. The one first is Trio Shield Trio. Even though I haven’t heard much about it (yet), I’ve heard that some people compare it with putting water on your dog then expecting that to repel parasites. The second one is Sentry cat products. I’ve read several reviews that said they used permethrin even though it’s toxic to cats. (Even though it’s not on the list, it doesn’t have to be put there.) On top of that, a lot people reported ill-effects even after following instructions.

  21. Pam grimes

    With all my dogs, some very allergic I have never had any problems with Heartguard. I only use a small drop of frontline for fleas if they have one. That is extremely rare. I tried a non pres. brand once and they got sick and allergic. Never use a flea collar.

  22. Margaret

    Has anyone had any experience using simparica?

    1. Paula Stewart

      Watched my 5 year old german shephard have his second seizure today. Gave him samparica yesterday. He seems fine for now.

      1. Rocky

        That’s upsetting! Is he okay? I’m trying to figure out how to proceed. Guessing I’ll just stay with Advantix and sentinal chewable.

      2. Steve

        Gave my Yorkie 1st time and she got sick with bad tremors and muscle spasms
        I took her to vet and he said he did not think it was med but rather inflamed disc in back
        I gave her second dose about one month later and same thing happened
        Bad muscle spasms and severe seizure like jerking and vomited
        I am so sorry I didn’t put it together and I will never use samperica or any other oral
        Will try some topical after I research
        She is getting better on day 3

        1. Jennifer

          We gave our poodle-mix her second dose of Simparica o Monday night. By early Tuesday morning she was having a seizure and had another one at noon. We spoke to several vets and have even seen a neurologist, but no one wants to blame the Simparica. My husband and I do, though. It has been 4 days since she was given the second dose, and even on phenobarbital she is still having twitches and tremors. We will NEVER give her Simparica (or any other like treatment) again! Does anyone have any reports of what happens to affected dogs after the dose is out of their system? We are hoping against hope that once this month passes that the seizures will go away. We would appreciate any feedback if you have had a similar experience.

      3. Jennifer

        Our dog Gigi had two seizures hours after his second dose of Simparica. She is now on phenobarbital and even on that she is having daily head tremors. Did your German Shepherd eventually get better? I surely hope so. It has been 48 days since her last dose of Simparica, and we are hoping against hope that her side effects from the poison will go away.

    2. christy

      yes and she died tonight in the hospital after taking it for the first time!!!! We are devastated and will be calling company Zoetis tomorrow to let the know they killed our furbaby!!!

      1. Ang

        So very sorry for your loss Christy, what a horrible way to end the life of your furbaby, you obviously cared greatly for or you would not have been trying to prolong her life, by treating for heartworm and fleas. Hugs to you and yours.

    3. Michelle

      My pup Riley is now being treated for non Regenerative Anemia after a dose of Simperica….it is a nightmare! Please do not give any of these meds to your dog! I will have to live with the fact that I did this to her for the rest of my life.

  23. Cher

    Yes, had a bad experience with Simparica. Our dog 14 yrs old has always been healthy. Yearly vet visits. We have used frontline plus on her for fleas snd ticks for many years. Our vet switched her to simparica.our dog now has open wounds where she has bit and ripped her hair out. She has tsken only three doses (1 per month) the first two have caused this biting open sores, last dose she was vomiting and had diarrhea within 2 hours of taking it. We have spent close to 500 dollars treating her with antibiotics, antiitch and steroid pills. Will continue to keep a recovery cone on her until the Simparica clears her system. Could take about 72 days for all traces to be gone.

  24. Emi

    Thank you dr. Alinovi for the comprehensive oberview on the newest cheweble insecticides. Would you kindly also provide the literature where the information was extracted from. I’d linke to share your text with the original texts attavhed for thoroughness. Thabks you so much.

  25. KBinVT

    Frontline stopped working for ticks in my neck of the woods, so my vet convinced me to try Bravecto on my two dogs. One had a bad reaction to her first dose of Bravecto (vomiting, drooling, dark stools), so that was the end of that.

    All summer and into the fall I used only Springtime Bug-Off garlic tablets (daily in their food). Wondercide (applied at night before bed), and fastidious tick-checking on both dogs (and monthly Heartgard for heartworms). We live in a high tick area. A much lower number of ticks than usual did crawl onto the dogs, but most looked like they were trying to figure out how to get off the dogs after realizing they didn’t taste right. The few that did attach died before engorging. So far, no signs of any tick-borne illnesses in either dog; blood tests this spring will confirm/deny that fact. I intend to continue this regime starting in early spring, and will post back with results after the first tick barrage subsides!

  26. peggy

    my 3 month old yorkie is having seizures and at times completely out of it. he got his regular booster and 2wks later got another booster and kennel cough plus a sentinel pill.3 days after this he was salivating and had a seizure. we took him to the vet and they did the bile acid blood work and said it was a liver shunt. I believe that he was over dosed. I started making his food so it is low protein. he had been good for about 3 weeks then had a seizure again lastnight. it has only been 1 month since he had all that medicine. I don’t know how long it takes for that to get out of his system. the liver shunt surgery is very expensive and no guarantees that he would make it because he is 3 lbs. he still eats and goes out to the bathroom and knows who we are. I am just very frustrated because before all that medicine he was a normal puppy. any advice you can give would be great.

  27. HappyDVM


  28. Diane Furry

    This is great information to know. But now what. What do I give my dog for fleas and heart worm?

    1. Lianne Soucy

      I was thinking exactly the same thought…as well as ticks. I live in CT where we have Lyme disease…

  29. Sarah V

    3rd month on Simparaca, my girl is vomiting all the time, dark stools, can’t drink too much water or throws that up too! My gut said it was the meds but my Vet who I love insits it’s not. I hope she makes it thru this ok, no more for her. Any tips on getting them detoxed from this stuff?

    1. Jennifer

      Did you ever find out how to detox from Simparica? We gave our dog her second dose Monday night and by early Tuesday morning she was having seizures. We spoke to 5 vets, including a neurologist, and NONE will even entertain that it could be the Simparica. They say she would’ve had a reaction the first dose, but from what I am reading many dogs start reacting with the second one. We would love to detox her asap. Any info you could share would be most appreciated.

  30. lynn rosa

    DIATOMACEOUS EARTH ???? that can be applied topically. NOT ingested though. i know it kills current infestations, but not sure if it prevents. i’l look into this. I have used it before and it definitely KILLED fleas. as far as heartworm, and parasites…. that is another problem. plus, it probably kills ticks too.

  31. lynn rosa

    ALSO try Rose Geranium Oil. i heard that works wonders.

  32. Robin mason

    Does anyone know anything about Credelio? My vet gave it to me yesterday for my poodle/ shih-tzu mix. She said it was new… I am Leary of giving him anything that is ingested and the fact that it is new concerns me even more..

    1. drcathy

      The safe use of Credelio in breeding, pregnant or lactating dogs has not been evaluated. Use with caution in dogs with a history of seizures. The most frequently reported adverse reactions are weight loss, elevated blood urea nitrogen, excessive urination, and diarrhea. See package insert for full safety information.

  33. Becca G

    My Australian Shepherd was on Trifexis for 6 months and was completely fine. After putting him on Simperica and interceptor he started having seizures. I’m not using these ever again.

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