Two Easy Ways to Start Earning Rewards!
Become a member today!
Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
Already a member? Sign in
Become a credit card member today!
Earn 2X Pals Rewards points at Petco
when you use Petco Pay!
APPLY NOW
Learn More About Petco Pay Benefits

Can I combine flea meds after giving my dog expired Comfortis?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed Medium (23 - 60lb) | Female | spayed | 26 lbs

Hi there. My dog has a flea issue. Accidentally gave her expired comfortis last wed. She had a bath Thursday and I got a diff flea med. can I give that to her now since I'm finding more fleas or do I have to wait longer. I obv don't want to give her too much. Also can I use a seresto collar and the oral dose?

3 Answers

Most Helpful Answer

Answered By Kevin Sanada, DVM

Veterinarian

Published on September 3rd, 2017

Hi,

The truth about expiration dates is that they are usually not based on any studies and the drug is likely to be just as effective years after. I can't say for sure, but it's likely that Comfortis will work. However, the fleas should all be dead within 24 hours, so if you are still seeing live ones jumping around, then it likely didn't work well.

You can definitely use the flea collar with Comfortis and this may help to rid her of the remaining fleas. I recommend waiting another week after applying the collar to assess if the treatment worked.

If you are still seeing fleas crawling around, then you can try a different flea product like Frontline. Avoid any products that contain ivermectin or any other avermectins for at-least 4 weeks after giving the Comfortis - you can check for this by looking at the active ingredients on the package...any name that ends in "-mectin" should be avoided.

I hope that helps and Maggie if flea-free soon.

8Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Dr. Macartney, BVet Med, MRCVS
Veterinarian
I am sorry you are having a difficult time gettin on top of the deal problem. Fleas can be very tricky to control. Because you have recently used a comfortia treatment that was expired I would not advise using any other medication for the time being. It is difficult to know how Maggie's system will react to the experience medication and it is better for her health to not attempt any further medications and this complicate the matter further. Watch for signs of vomiting, dirrhoea, inappetance or changes to thirst or urination which could indicate she is not tolerating the medication well. I believe there most likely outcome is simply that the comfortis will be ineffective as it's past it's use by date.

You can switch to the seresto after one month from giving the comfortis. I would advise using either the collar or an oral medication and not the combination. Too much medication can overwhelm Maggie's system and may not be needed.

In the meantime, Remember that in addition to treating fleas and ticks on the animal, you also need to treat the pet's environment, indoors and out. Many indoor products contain both an adulticide (permethrins and pyrethrins) and ingredients to kill the eggs and larvae (Nylar ). Examples include Bio Spot® Room Fogger, Bio Spot® Carpet Powder, Bio Spot® Carpet Spray, and Bio Spot® Yard Spray. Fleas actually spend most of their life cycle off of a dog and so treating the home is very important.

When using foggers, you need to cover/seal fish tanks, and remove any birds, before using. Vacuum and wipe off counters/eating areas thoroughly after using any fogger.

Here is some information on how to treat your home and Maggie to get rid of fleas;

https://www.petcoach.co/article/5-tips-to-get-rid-of-fleas/

I hope that is helpful and please ask as many more questions as you may have on this topic. I am here to help!
3Pet Parents found this answer helpful
Answered By Vanessa Yeager DVM MPH
Veterinarian
Hello and thank you for your question on Petco Pet Education Center, formerly Petcoach!

Yes you can use a Seresto collar or a topical flea treatment. I wouldn't use both. I don't want to overload her system.

In case the comfortis was somehow still effective even after the expiration, I wouldn't give her another oral flea medication, but a topical would be okay: either topical or collar.

I hope this has helped answer your question! Best of luck to you and Maggie!
1Pet Parents found this answer helpful

Smart Picks for Smart Questions

Related Questions

My dog's Trifexis isn't working. Can I give Comfortis for fleas?

Hmm - it's odd that the Trifexis doesn't seem to be working as well, because it actually has the same active ingredient as Comfortis. The only difference is that it has an added ingredient for heartworm prevention, otherwise it's exactly the same drug. In my experience, both are extremely effective for fleas. I wonder if perhaps Tessa is continuing to pick up fleas from somewhere in the environment? It does take a few hours for a flea to die after biting her, so if she is continually being re-infested from the house or yard, it's very possible that you might see live fleas on her even if the medication is working properly. If you think this might be the case, I would recommend treating your house and yard with a premises spray such as Knock-Out. If you still want to get her something else for fleas, I would not recommend giving a Comfortis dose on top of the Trifexis, because this would just be giving a double dose of the same drug - I would be concerned about possible side effects from overdosing this medication. Instead, you could consider using a topical flea medication this month such as K9 Advantix, since this is a completely different medication that doesn't interact in any way with the Trifexis.

Updated on September 23rd, 2025

Health & Wellness

Advantage not working for cat fleas. Can I switch to Comfortis?

Hi there. I think your plan of using Comfortis instead is a good one. If you opt to do this, there's really no need to give the Capstar first, as the Comfortis will start working quickly on its own :) You can go ahead and do this now - the Comfortis should not have any harmful interactions with the Advantage, even if it was only applied a week or so ago.

Updated on September 23rd, 2025

My dog has fleas despite Comfortis and Hartz collar. What to do?

Thanks for using Petco Pet Education Center, formerly Petcoach! While it is ok to use both, I would suggest a different approach if you are still finding fleas on Daisy. I would try a product called Capstar which can kill a lot of fleas at once and combine it with another monthly flea preventative other than Comfortis if you are not seeing the desired results currently. I would suggest products such as Frontline and Bravecto which are great. Good luck and have a great night!

Updated on September 23rd, 2025

My dog still has fleas after Comfortis. Why is she still scratching?

Comfortis is a great product and should start killing fleas within 30 minutes. If you are still seeing fleas there are a few things to consider. First, make sure you give the Comfortis on a full stomach and make sure the dog keeps it down (sometimes dogs vomit after taking it). There are also probably fleas in the environment/home. I would recommend vacuuming all carpeted areas in your house and washing all of the pet's bedding. Even with the best flea control it can take up to 2-3 months to get the flea problem under control. Make sure you treat all the other pets in the household as well

Updated on September 23rd, 2025

What tick prevention can my dog use with Comfortis for fleas?

You can use a Preventic collar, a Seresto collar, or a topical medication such as Frontline or K9 Advantix along with Comfortis for tick coverage. Or, if you prefer to stick with oral medications, you can switch from Comfortis to Nexgard or Bravecto - both of these cover both fleas and ticks, and are also very effective.

Updated on September 23rd, 2025

My dog vomited Comfortis 2 hours later. Is the pill still active?

Yes, as long as he doesn't vomit within 1 hour it should be effective. Always remember to give it with a meal. If he continues to vomit after the 3rd dose of Comfortis, switch your product. Thank you for using Pet Coach.

Updated on September 23rd, 2025

Dog has fleas on Seresto. Can I use Capstar & switch to Frontline?

Hello! I'm sorry to hear that Bliss is still struggling with fleas. They can be really hard to get rid of! It is usually safe to give Capstar with Seresto, but if your dog has any medical conditions, I highly suggest that you contact your vet first. Seresto and Frontline used together should not interact, but it's never a bad idea to wait a day or two between removing the collar and applying the Frontline. This is my suggestion for your next few days: First, give Bliss a good bath. I do not recommend using any flea or tick shampoos - a regular dog shampoo or baby shampoo should do the trick. Leave the soapy lather on her skin for several minutes before rinsing, and use a flea comb to get rid of as many fleas as possible. Next, give Bliss the Capstar. Immediately after, be sure to wash all her beds on the hottest cycle. Beds that can't be washed should be dusted with diatomaceous earth or borax powder (away from pets). You can do this with carpets, too. Let the dust sit for an hour, then vacuum everything really well. Borax and diatomaceous earth should not harm your pets, but it's best that they don't ingest a lot of it, so try to keep them away while you do this. Throw away your vacuum bag or toss the contents outside in a dumpster right away. If Bliss is an outdoor dog, I highly recommend spraying the yard with an outdoor flea and tick killer, like Advantage Yard and Premise Spray. These cleaning steps are really, really important as the flea life cycle allows flea larvae to live and eat off of fibers in your home for 3 weeks. You should do this cleaning step again in 2 weeks to get any remaining flea eggs or larvae. After 24 hours, apply the Frontline. You should always wait 24 hours after a bath to apply Frontline as the natural oils in the skin need to regenerate before it will work properly, and bathing removes these oils. It is not unusual to see fleas on your dog even after this process, at least for a few weeks. Fleas only jump on your dog to feed, which is when they will come into contact with the Frontline and within 24 hours. Any fleas or larvae remaining in the home will eventually find their way to Bliss, but the Frontline should get them. If these steps don't work, it's time to involve your vet, and possibly a flea removal specialist, like Orkin. I really hope that Bliss is flea-free soon!

Updated on September 23rd, 2025

Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Share