PetMeds® Frontline Plus Questions

Some of the more common recent questions I’ve received in the clinic regarding f and its use for flea and tick prevention in pets. A big concern I often receive is the quality of Frontline Plus being carried by online pharmacies like 1800petmeds and whether it is the same as those used and sold by veterinary offices. The truth of the matter is that Frontline Plus is a prepackaged product by Merial, and is the exact same one carried by 1-800-PetMeds as your local veterinarian. Improper application is one of the most common reasons for flea treatment failure

Another common question is, “Why does my pet still have fleas after applying Frontline?” (after a few consecutive months. The most common reasons for flea treatments failing is typically because of improper application, or more commonly failure to treat the environment of the pet, including the home and yard; where 80% of the flea life cycle occurs. Along the same line, some products, however will work better on some pets than others. So, if there are still fleas even after properly treating the home and using Frontline Plus for several months, I would suggest having your house professionally treated by an exterminator and/or change to a different product such as Advantage.

If a pet still has fleas, many veterinarians will use the product more frequently than once monthly, sometimes as often as once every 2-3 weeks. However, this process is often considered to be “off label use,” and I would not use the product this way unless first speaking with your pet’s veterinarian. If a client is currently using a different topical such as Revolution or Advantage, it is safe to change to Frontline Plus after 3-4 weeks from the date of last application of the other product. While Frontline Plus is labeled as waterproof, I usually advise clients to wait at least 24 to 48 hours before bathing their pet. Side effects to Frontline Plus are rare but may include hair loss/skin irritation at site of application, (rarely) digestive upset, (and even rarer) immunological reactions of the blood or neurological reactions like seizures. Again, these are very rare, as most pets tolerate this product quite well.

Related Posts


  1. I have to treat 2 cats with Frontline for the first time. What if one of them gets in contact with the Frontline that I applied on the other cat.

  2. Dr. Michael Dym, VMD veterinarianJanuary 9, 2014 at 1:42 am

    Try to prevent this by keeping them apart for a few hours. If in doubt of exposure have vet assessment

  3. I used Frontline Plus for several yrs on my 3 cats. After noticing that frontline’s effective had decreased I have been using Advantage ll for about a yr. I still have a supply of frontline and would like your opinion if frontline’s effectiveness may return after a yr of non-use on my cats. Also would it be ok to use frontline one month and advantage the next month. Maybe like that the fleas would not become immune to either. Any thoughts?

  4. Dr. Michael Dym, VMD veterinarianJanuary 23, 2014 at 3:44 pm

    No problem alternating flea products monthly. I dont think this issue has ever been studied.

  5. I have 3 cats all inside/ outdoors. As soon as they got fleas this summer I bathed them and waited 2 days till I applied front line plus for cats. My long haired kitty still has them crawling all over, its been 8 days…the other 2 seem better but I’ve seen some on them 2 just not as many. I have not seen a flea in my house and I wash everything once a week. Should I wait the remainder of the 30 days and apply another dose or try something else? I don’t want him to suffer the fleas or possibly get tapeworm.

  6. Dr. Michael Dym, VMD veterinarianJune 13, 2014 at 6:45 pm

    I have found front line not as effective as it used to be in some cases, as well as people often forget to treat the environment or home of pets, where most of flea life cycle occurs. I would try a different product like comfortis from 1800petmeds.

  7. I used wilkos own flea treatment on my cat 3 weeks ago and it’s not done a thing. Can I use frontline so soon or wait another week? Thanks in advance

  8. Never mind due tomorrow. Thought I.would get a quick reply

  9. Ernestine JosephJuly 1, 2014 at 2:59 am

    i used a Hartz ultra Guard on my 37 then i realized it stated on the tube ‘for dogs over 60 lbs’ should i bathe him right away to take the il off? . is my dog going to break out out? is he going to be okay?

  10. Ernestine JosephJuly 1, 2014 at 3:02 am

    i used a ultra gaurd on my 37lb. dog then i read the tube (which i should have done 1st) and noticed it stated for ‘dogs over 60 lbs.) will my dog be okay? will it make him sick? should i bathe him and take it off?

  11. Ernestine JosephJuly 1, 2014 at 3:04 am

    i used an “ULTRA GUARD on my 37lb dog…then i noticed the tube says ‘FOR DOGS OVER 60 LBS. will my dog be okay?

  12. Ernestine JosephJuly 1, 2014 at 3:05 am

    i used an “ULTRA GUARD on my 37lb dog…then i noticed the tube says ‘FOR DOGS OVER 60 LBS. will my dog be ok

  13. Can I apply frontline right after my dog’s bath or do I have to wait

  14. Dr. Michael Dym, VMD veterinarianAugust 6, 2014 at 2:20 pm

    Although it is supposed to be water proof, I usually wait 48 hours after application to bathe your pet

  15. I have always used Frontline on my two cats with no problem but this summer it has not worked at all for the last three applications.It seems to have no effect whatsoever on the fleas. I have treated the house. Can I use another treatment before waiting four weeks and which would you recommend?

  16. Dr. Michael Dym, VMD veterinarianAugust 9, 2014 at 2:26 pm

    I would try another product like oral comfortis from 1800petmeds.

  17. I applied hartz spot treatment to my dogs 8 days ago. Didn’t work and of course I would have used if I had known. I’ve bathed them 3 times with Dawn within 3 days following. I have them a capstar that worked for the 24 hours but they are itching again. We are getting in a car for a 15 hour drive to move. Can I give them advantix and a cap star before we get in the car 10 days after the hartz so we make sure we do t take any fleas with us?
    I do t want to make them sick or hurt them with to many chemicals. We are bombing the house which will be empty for awhile but we do t want to take any fleas with us they are small dogs

  18. Dr. Michael Dym, VMD veterinarianAugust 10, 2014 at 2:54 pm

    I dont think you have a choice but to use another flea medicine like advantix, as well as capstar as needed to treat adult fleas.

  19. I have used Frontline and Advantage off and on for my golden retriever with average success. In the area we live my vet says that over the past years the fleas have built up resistance to both drugs. 2 years ago my dog developed cancer, Mast Cell Tumor, Grade II Stage. We only found one tumor and had it successfully resected with wide margins and to date no other tumors. At the time of diagnosis I stopped all topical flea treatments and only occasionally used Capstar through the warmer months in Coronado, CA (San Diego). This summer however in uncommon humidity we are having a horrible time with fleas and I have done Everything non systemic. I have two vets and one oncologist and they all want to give comfortis or some other oral pesticide. I am frankly concerned about giving oral pesticides of this magnitude to a cancer dog with an already compromised immune system and have read hundreds of bad reviews about comfortis as well as the new Seresta (sp?) collar. Any other treatments or thoughts come to mind? Thank you!

  20. Dr. Michael Dym, VMD veterinarianAugust 17, 2014 at 2:16 pm

    With a history of mast cell cancer, I would try natural flea treatments like the one from vetri science, which you can google on line, as well as or It also may help to consult with a holistic veterinarian. If you have to use chemical preventatives, I would consider topical revolution, which I find safest of the bunch in my opinion.

  21. thank you so very much, I appreciate your opinion. Someone mentioned Skin So Soft Oil diluted half half with water, an Avon Bath oil with side effects of a bug repellent is also affective on dogs. I have been using this with success over the past few days if I spray him before and after our walks. If I go to another topical I will try Revolution which I have never tried before. I have tried Wondercide flea repellent and my golden seemed to have a reaction to it – very lethargic, seemingly depressed and a bit sick overall. A holistic vet is also an option, but I would be surprised if they could suggest anything holistic I haven’t researched and tried over the past few years, and I am not in a hurry to a fourth vet to our mix, it’s hard enough juggling 3 with different opinions! 🙂 Thank you again for your response, I will look for the vetri science treatment online.

  22. One last question, the Vetri Science topical you mention above contains 9.7 % Fipronil which is the same ingredient as Frontline – 9.8% Fipronil. Is there something I am missing about “the natural” recommendation you mentioned or is there a different flea treatment you were referring to from Vetri Science? Thanks again.

  23. Dr. Michael Dym, VMD veterinarianAugust 18, 2014 at 9:31 pm

    Hi Caroline. I am not familiar with fact that vetri science is using a fiprinil based product. As far as I knew it was an essential oil and/or cedar product. I would contact the vetri science company directly for clarification on this issue.

  24. Dr. Michael Dym, VMD veterinarianAugust 18, 2014 at 9:32 pm

    Hi Caroline. Also consider some of the great natural products for flea/tick control from my friend Bill, owner of

  25. Help! My almost 18 year old healthy golden cocker lab terrier mix is infested with fleas. She’s been on frontline advantage advantix all her life and it’s never been this bad! It’s 25 days into the month and I’m wondering if I can give her August 29th application today? I’ve washed her and her linens and sprayed them along with the house using natural products. I brush her several times an hour and the more I brush the more fleas I find. Your advice would be greatly appreciated. Thank you do much!

Leave a Comment