Frontline Plus: An In-Depth Review

Flea & Tick


Nathan Hinds


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Frontline Plus

Stroll down the flea treatment aisle at any pet store, and there’s no doubt you’ll come across Frontline Plus.

Standing on the front lines of the battle against pests for pets since the 1990s, the Frontline brand is a staple of the flea treatment and prevention market.

Frontline Plus, as the name implies, improves upon the original product (Frontline), and it is designed to take fleas out before they reach maturity. 

In this article, we’ll take a closer look at Frontline Plus, beginning with its origins two decades ago. We’ll examine the active ingredients, consumer reviews, safety issues, and everything in between – we’ll help you decide if Frontline Plus is the right flea-fighter for Fido! 

Frontline Plus: Key Takeaways

  • Frontline Plus is a topical, over-the-counter medication designed to kill fleas, ticks, and lice.
  • You administer Frontline Plus once per month, by squirting the fluid directly on your dog’s skin, between his shoulder blades.
  • The active ingredients in Frontline Plus — fipronil and s-methoprene — are largely considered safe and effective for most dogs.

Frontline History & Background

The Frontline name has been at the forefront of protection against fleas and ticks for more than 20 years. Manufactured by Merial and armed with the powerful ingredient fipronil, this robust treatment and preventative works fast and efficiently.

In the year 2000, Frontline Plus hit the market, combining the benefits of Frontline’s existing flea and tick protection with an ingredient called s-methoprene.

This new addition was included to ensure fleas don’t make it past the larva stage, stopping an infestation dead in its tracks. The all-inclusive Frontline Plus kills ticks, fleas, and lice, and just one dose keeps your pooch protected for 30 days.  

frontline plus

Frontline Plus Basic Overview

Frontline Plus is a preventative flea medicine for dogs of all sizes that are older than 8 weeks.

You can select the product from one of 5 weight categories, starting at 5 pounds and accommodating up to 132 pounds. Once applied, it’s effective at killing fleas, lice, and ticks – it also breaks the life cycle of fleas, interrupting the development of the eggs and larva before they reach maturity. 

The medicine comes in a plastic applicator tube, which is easily snapped open for application to your pup’s shoulders. For continued protection, it’s advised that you reapply it once each month.

You’ll want to avoid giving your dog a bath for at least a day afterwards, and avoid petting the area where it’s applied for a day or two as well.

Be sure and discourage any rolling or scratching after the application, and if your dog has canine friends, avoid roughhousing for a bit to allow the medicine time to seep into the skin. 

As with any other medication, be sure to administer Frontline Plus in the exact manner described by the label or product literature.

What’s in the Frontline Plus Box?

There isn’t a whole lot included in a box of Frontline Plus. Essentially, you’ll get some informational paperwork and a few individual doses contained in small tubes.

The number of doses included in the box varies. We’ve seen boxes that contain three, six, or eight doses, and it is possible that you may encounter other quantities.

Inside each tube is a mixture of active and inactive ingredients. The active ingredients are the firepower of the product — the ones that do the heavy lifting. This is the stuff that makes the product function as advertised. In this case, it’s the flea-killing, tick-zapping substance. 

The active ingredients in Frontline Plus include:

  • Fipronil (9.8%)
  • (S)-Methoprene (8.8%)

The inert ingredients make up everything else. They help do things like preserve the product and make it easier to apply to your pet.

Because these ingredients are pretty inert, Merial doesn’t have to list them on the product packaging. So, we can’t tell you what exactly they include. This may seem frustrating, but it is a pretty common practice among flea medication manufacturers.

How Does Frontline Plus Work?

You may be surprised at how simple the application instructions on the Frontline Plus box are: Simply open the package and squeeze all of the contents onto the skin between your pup’s shoulders (be sure to part the hair so the medicine gets down where it needs to be). There’s no need to rub it in, and no reapplication is necessary for 30 days.

The secret to its full-bodied effectiveness is called “translocation.” 

Basically, once the product is applied, it quickly collects inside your pet’s oil glands. Over the course of the next month, the product continuously seeps out through the oil glands all over your dog’s body, so he’s covered from head to tail with a thin and consistent layer of flea killer. 

The fipronil ensures that adult fleas are killed as soon as they touch your pooch. The s-methoprene has a similar effect, but on the flea eggs and larva – it stops the growth of fleas before they reach maturity and can bite your dog. 

Frontline Plus also kills ticks that may attach themselves to your dog. However, it does take about 24 to 48 hours to do so, so you’ll still want to be sure to check Fido for ticks following outdoor adventures.

Is Frontline Plus Effective?

No flea treatment is perfect, and their efficacy can vary a bit from one situation to the next. Having said that, Frontline Plus appears to be effective in most situations.

Generally speaking, the peer-reviewed literature reflects as much. For example, a 2011 study found that:

“…in field situations FRONTLINE® Plus provided effective flea control, as assessed by the significant decline in flea emergence from the contaminated household.” 

However, the scientists performing this study didn’t compare Frontline with any other flea treatments.

Another 2011 study produced even more impressive results, with the scientists finding that:

“dogs treated with FRONTLINE Plus had 100% efficacy at the 12, 18, and 24 hour assessments on day 1 post treatment, and on days 7, 14, and 21 post-infestation. On day 28, 100% efficacy was achieved by 24 hours post-infestation, and efficacy was >99% at the 12 and 18 hour time points.”

However, in the case of tick control, a 2003 study found the Frontline was less effective than K9 Advantix:

“Percent efficacy for the K9 Advantix group ranged from 84.0 to 98.5 % between test days 3 and 35. Percent efficacy for the Frontline Plus group ranged from –28.1 to 56.8% during the corresponding period.”

We also found a few additional studies that examined of other flea treatments that use the same active ingredients (fipronil and s-methoprene).

By and large, they also demonstrated that this combination of ingredients is very effective:

A 2016 study of dogs in India found that it:

showed variable efficacy against ticks (34.00 to 65.48%) and high efficacy against fleas (100%) for a month. The results demonstrated the overall high level of efficacy of spot-on formulation against ticks and fleas in naturally infested dogs, as previously reported for fipronil and (S)-methoprene.

A 2004 study of 32 flea-infested beagles found that:

Based on larval hatch (Table 1), excellent control (>95% efficacy) was achieved with the fipronil/(S)-methoprene combination product and (S)-methoprene alone for 6 and 5 weeks, respectively. Excellent control of adult flea development was achieved with the combination product and (S)-methoprene alone for at least 8 and 6 weeks, respectively. “

A 2008 study concluded that this combination of ingredients was not only effective, but that it was more effective than permethrin-based products. As explained by the researchers:

“Overall, in this study the combination of fipronil/(S)-methoprene provided consistent and high levels of efficacy against fleas and ticks throughout the entire month, significantly superior to that of either imidacloprid/permethrin or imidacloprid alone.”

Just understand that while Frontline Plus is effective against fleas, there are likely better tick-killing options available for specifically protecting your dog from these eight-legged disease vectors.

Is Frontline Plus Safe for Dogs?

As we’ve discussed, the active ingredients in Frontline Plus are fipronil and s-methoprene. Unsurprisingly, these ingredients aren’t exclusive to flea and tick prevention in dogs and cats. 

Fipronil is used in many different anti-bug products, such as pesticides for your lawn or for farmers’ fields. Pesticides may sound like something that you want to keep away from your pet, but don’t worry — scientists generally agree that topically applied fipronil is safe for dogs.

From a 2014 study published in the journal Biomarkers in Toxicology: 

“The USEPA has determined fipronil to be safe for use on dogs and cats, with no harm to humans who handle these pets. Most of the time poisoning cases of fipronil occur in dogs and cats due to accidental ingestion of the product Frontline. “

It is important to prevent your dog from ingesting fipronil, but that’s part of the reason it is typically applied to your dog’s neck or shoulder region, which is hard for him to reach with his mouth. 

S-methoprene, the other active ingredient in Frontline Plus, is a chemical found in products like household bug spray or other insecticides. In fact, it’s even used in some livestock foods to keep it pest-free. 

This chemical basically goes undercover and acts like a growth hormone to fleas and other insects – but instead of accelerating affecting growth, it stops the biting bug’s development cold.

Like fipronil, it appears that s-methoprene is safe for most dogs.

Unfortunately, there isn’t much information available regarding the safety of s-methoprene in isolation. However, a 2013 study published in Journal of Veterinary Science & Technology examined the safety of a similar flea and tick treatment that also contains fipronil and s-methoprene (Biospot). 

During their work, the researchers concluded that it:

“…was found to be safe for topical application, as none of the dogs showed any adverse effects, and no skin reactions occurred at the application site.” 

Does Frontline Plus Kill Dogs?

There are scattered reports online — primarily shared via social media channels — explaining that Frontline Plus has sickened or even killed dogs.

However, it is important to keep these anecdotal reports in perspective. They rarely include all of the information one would need to properly assess the situation, and veterinary documentation positively linking Frontline Plus (or the active ingredients it contains) to serious illness is similarly rare.

However, the EPA did investigate the safety of several topical, one-spot flea treatments in 2009. During their study, they did find a small number of “major incidents” and pet deaths occurred.

Nevertheless, the EPA specifically states that:

…the products could be used safely but that some additional restrictions are needed.

They go on to state that proper administration is imperative, and that it is very important to dose your dog correctly.

The reported incidents demonstrated that many but not all pet incidents took place because the products were misused, bolstering the need for clearer labeling.

So, what is the takeaway for owners? We’d suggest the following:

  • Always consult your vet before giving your pet any flea and tick medication.
  • Be careful to follow the instructions provided to the letter.
  • Make sure you have an accurate weight for your pet before purchasing a flea and tick medication.
  • Small dog owners should use extra care. Many of the most serious cases examined by the 2009 EPA study involved dogs weighing between 10 and 20 pounds. Chihuahuas, dachshunds, miniature poodles, and shih tzus were among the breeds who seemed to experience problems most commonly.
  • Stop using any flea and tick medication and contact your vet if you note possible side effects, such as skin irritation, gastrointestinal upset, uncoordinated behavior, drooling, difficulty breathing, or lethargy.

We’d also recommend that once you find a good dog flea and tick medication that your pooch tolerates well, you don’t change it unnecessarily.

Before moving on, we’ll leave you with the comments of ASPCA veterinary toxicologist and senior vice president for animal health services, Dr. Steven Hansen following a 2009 study:

The important take-home message is that although adverse reactions can occur with all flea and tick products, most effects are relatively mild and include skin irritation and stomach upset.

Is Frontline Plus Safe for Humans?

We’ve allayed your fears for your pet’s well-being when it comes to the ingredients in Frontline Plus, but what about your own?

It’s probably a given that when applying this messy product as directed, you’ll get a bit on your hands. While you’ll certainly want to wash up afterwards, there’s no need for major concern.

You’ll want to keep your flea treatments away from children and your pets so they don’t accidentally play with it or ingest it – and, for goodness sake, you’ll want to avoid eating it as well. 

According to the National Pesticide Information Center, fipronil is pretty harmless to us humans in small amounts. If ingested, you’ll want to seek medical attention (at the very least, give your doctor a call), but odds are there won’t be lasting effects. 

The NPIC reports similar information on s-methoprene – while consumption in large doses for people is unwise, the occasional brush with the product is not generally cause for concern.

In fact, this chemical is allowed to be in a lot of common foods that you eat (which is kind of gross, but probably less gross than finding bugs in your food). 

Frontline Plus Pros and Cons

Now that we’ve tackled the basics and the background of Frontline Plus, let’s delve into the pros and cons to help you decide if it’s the right preventative and treatment for your pooch:


  • Frontline Plus is an all-in-one option, ticking the boxes for both treatment and prevention. You’ll save time and money with this one-stop shop. Most importantly, the preventative nature of Frontline Plus will spare your pet discomfort by avoiding recurrent flea attacks.
  • With Frontline Plus, you can plan ahead. One dose at the beginning of the month, and there’s no need to worry about fleas, ticks, or lice for 30 days. Matched on the calendar with other important monthly preventative measures like heartworm pills, it’s an easy and convenient way to keep your pooch pest-free. 
  • Frontline Plus kills fleas on contact. Other treatments require fleas to bite before they take effect. While those fleas won’t be repeat offenders, the damage is done by the time they’re dead. Frontline takes them out before they get a chance to cause discomfort. 


  • The application process can be a bit tricky. You’re tasked with keeping your dog still while you open the tube and apply to the shoulders – trying to keep it off your hands or your carpet can be challenging. If possible, you’ll want a friend to help out.
  • It doesn’t kill ticks very quickly. While Frontline Plus does kill ticks, it doesn’t always do so quickly enough to prevent the bloodsuckers from transmitting diseases to your dog. 
  • Prevention isn’t free, and neither is Frontline Plus. While proven to be effective, it’s on the high end of the price spectrum. While it may save you money by avoiding the potential costs of flea shampoo, vet visits, and treatment if you encounter a flea infestation, prevention is still an investment. 

Frontline Plus Rating

Overall, we give Frontline Plus four stars out of five. 

If you’re dealing with a nightmarish flea infestation, Frontline Plus is an excellent option. 

Powerful ingredients that kill on contact are a high-powered line of defense for your pup and proven effective at getting the job done. Satisfied customers report that the convenience of the 30-day span of the prevention is helpful for adventure-loving pups who love spending hours on end in the outdoors. 

Perusing reviews about Frontline Plus, you’ll see a variety of responses – some pet owners say that it works like a charm, while others claim it’s completely ineffective.

For those negative reviews, we can’t say we know that the product was applied properly and directions were closely followed — but it’s important to consider a variety of viewpoints when you’re picking out a product. 

Frontline Plus

Frontline Plus

  • Provides month-long protection from fleas and ticks
  • Kills adult fleas, larvae, and eggs
  • Available for dogs in 5 different weight categories
  • No prescription required

Final Thoughts

Regardless of whether or not your pup spends hours outside or goes to the dog park and doggy daycare, a trustworthy flea preventative is a must.

Fleas are a constant threat to your pet’s health and well-being – prevention should be a top priority, and it’s not a bad idea to have a treatment plan in mind in case you deal with an infestation. 

Frontline Plus is definitely worth a shot – before, during, or after a run-in with an insect problem. It’s hard to top the preventative protection that Frontline Plus offers, and the convenient once-a-month dosage.  

Just remember to discuss your flea-treatment choice with your vet. Even though Frontline Plus is available over-the-counter, it is always important to keep your vet in the loop when choosing a parasite-prevention product for your dog. 

If you don’t like the idea of Frontline, there are many other options such as flea collars and tick collars which can also function as a preventative.


Have you had flea-fighting success with Frontline Plus? Have another tried and true pest prevention plan? Let us know in the comments!

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Written by

Nathan Hinds

Nathan Hinds is a professional pilot, writer, and an avid animal lover. He is passionate about animal rescue and is involved in both fundraising and fostering. Nathan is a lifelong resident of St. Louis, MO and is the proud parent of a senior beagle mix named Gilmore, as well as a whole bunch of cats.

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  1. Dog owner Avatar
    Dog owner

    Back in 2019 I was using K9Advantix for about a year with no significant results. With no luck there, I went to using vet prescribed flea solutions for a few years – expensive. Thought I might try an over the counter solution again. I picked up Frontline Plus, the right dosage for my little dog, and I bathed my dog , visually made certain there were no fleas on him, then I applied the Frontline flea medicine, per directions. 48 hours into this, my dog is scratching constantly again (cannot get more than a few minutes sleep at a time) and I can see fleas again on him (he is an inside/outside dog and loves the grass). He seems to have tolerated the medicine well but it just isn’t working from what I can see. Your article states that there is 100% effectiveness of Frontline at 24 hours. I am not seeing any effect AT ALL at 48 hours and my little dog is miserable. And now, I cannot dose him with anything else for 30 days, according to the packaging. I guess I am back to flea baths every other day.

    1. Ben Team Avatar

      Hey there, Dog owner. We’re really sorry to hear about your battle against fleas — it is perplexing why none of the top-tier OTC solutions seem to be working for you.
      We’d recommend going back with the vet-prescribed option if that worked.

      A quick point of clarification: We are not saying that Frontline is 100% effective after 24 hours — a study published in the International Journal of Applied Research in Veterinary Medicine did.
      You can check that link to see more.

      At any rate, we wish you the best of luck!

  2. Sally Hill Avatar
    Sally Hill

    Well done article! Thank you so so much!

    1. Ben Team Avatar

      Glad you liked it, Sally!

  3. Deanna Cheryl Avatar
    Deanna Cheryl

    I’ve been using front line plus consistently for years. My dog got a tick disease anaplasmosis recently. Almost died and cost me over 2 grand in vet bills not to mention emotional stress. Im returning the unused vials and never getting again and would not recommend ever.

    1. Ben Team Avatar

      So sorry to hear that, Deanna!
      Frontline Plus does kill ticks, though it takes some time to do so, which gives the little arachnids time to transmit disease in some cases.
      Check out our article on the best tick treatments for dogs to see some other options.
      Best of luck — hope your pooch recovered OK!

  4. Diedre Plude Avatar
    Diedre Plude

    What product will last for 1 yr?

    1. Ben Team Avatar

      Hey, Diedre.
      I don’t think there are any options that’ll last that long, but Bravecto provides three months of protection.
      Best of luck!

  5. Bonnie Handzlik Avatar
    Bonnie Handzlik

    I’ve used Frontline, then Frontline Plus, ever since it came on the market and always got 100% results. My last dog passed away in 2018, and I haven’t yet gotten another dog. But I’m being asked for a recommendation, and I’m now seeing lots of comments online that Frontline used to work great but no longer works since it was bought out by an overseas company, and also since it went over the counter-I always got mine from the vet by prescription. Do you know anything about this? I feel uncomfortable recommending a product I haven’t used for several years and no longer requires a prescription.

    1. Ben Team Avatar

      Hey there, Bonnie.
      Scads of owners use Frontline and find it effective. We wouldn’t hesitate to recommend it to our readers.
      That said, you can check out some alternative flea and tick medications here.

      I’m a fan of Advantix, but that’s because I prioritize tick prevention.
      Best of luck!