Frontline Plus For Cats: Overview, Dosage & Side Effects - All About Cats (2023)

Frontline Plus For Cats: Overview, Dosage & Side Effects - All About Cats (1)Frontline is a brand of topical, “spot-on” flea/tick treatment and prevention containing the ingredient fipronil. The patent on fipronil expired in 2010, leading to the release of many generic products. Frontline has since become only available as the products Frontline Plus and more recently, Frontline GOLD.

Frontline Plus For Cats Overview

Frontline Plus For Cats: Overview, Dosage & Side Effects - All About Cats (2)

Medication Type:

Phenylpyrazole antiparasitic


Topical liquid solution

Prescription Required?:


FDA Approved?:

This topical medication is approved by the EPA for use in cats.

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Life Stage:

8 weeks of age or older.

Common Names:

Fipronil, (s)-Methoprene

Available Dosages:

Single dose size for cats and kittens weighing 1.5lb or more.

In this article, you’ll learn specifically about the Frontline Plus product for cats, the ingredients it contains, what types of parasitic pests it targets, possible side effects to consider, and some frequently asked questions.

If you’re looking for a broader article on all Frontline products, see our article Frontline for Cats.

About Frontline Plus For Cats

Fipronil is the primary active ingredient in all Frontline products for both dogs and cats. It is indicated for treating fleas, ticks, and chewing lice. It can also kill mosquitoes. While not labeled for it, it has also been successful in treating for chiggers and the sarcoptic mange mite.

Fipronil is a phenylpyrazole antiparasitic agent, and is technically classified as a pesticide. In invertebrates (including insects like fleas and arachnids like ticks and mites), it interrupts GABA-regulated nerve channels, causing neurologic overexcitement, disruption and death.

Frontline “spot-on” flea and tick treatment products are applied to the surface of a small target area or “spot” of the skin, usually at the back of the head or neck.

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Fipronil collects in the oils of the skin and hair, allowing for continual release, lending to its 30 day period of efficacy for flea and tick protection. Per the product label, it takes about 24 hours to spread throughout surface oils on skin and hair to provide complete protection.

It is important to note that while these pesky pests are affected by Frontline by coming in contact with the skin and don’t have to actually bite a kitty to die, Frontline products do not provide true repellency that would prevent fleas or ticks from coming in contact with a pet.

What Does Frontline Plus Do For Cats?

Frontline products are among the only topical “spot-on” options for cats providing protection against both fleas and ticks. Other products for cats may only protect against fleas and some ticks, or just fleas.

Frontline Plus specifically includes the addition of (S)-methoprene, which is an insect growth regulator that additionally controls the flea life cycle by targeting flea eggs and flea larvae, helping to interrupt the life cycle and prevent new adults from hatching and developing.

Side Effects Of Frontline Plus For Cats

Frontline Plus For Cats: Overview, Dosage & Side Effects - All About Cats (3)

Most flea-infested cats develop dermatitis, withhair lossand itchy skin especially over the lower back, around the head, and elsewhere.

When used properly, side effects to Frontline products are uncommon. Frontline Plus for cats is only labeled for cats older than 8 weeks of age. Topical products like Frontline should never be ingested.

The most commonly reported effect is a temporary irritation at the application site. More red, irritated skin has been reported, but is considered rare. If this occurs, it is more likely a kitty has a hypersensitivity or allergy to one of the ingredients.

If this occurs, the manufacturer recommends bathing with a mild soap (Dawn dish soap for example) and rinsing with lots of water. Veterinary care should be sought with any persisting or worsening signs of skin irritation.

Both ingredients found in Frontline Plus (fipronil, (S)-methoprene) generally appear to have a low potential for toxicity both topically and even if accidentally ingested.

However, the products are very bitter tasting. If a kitty were to lick recently applied Frontline Plus off either themselves or a housemate, the bitter taste alone can lead to excessive drooling, agitation, and sometimes even vomiting.

According to DVM360’s article “Toxicology Brief: The 10 most common toxicoses in cats” this effect is typically not a true toxicity, but a sometimes dramatic reaction to the bitter taste. Providing milk or liquid from a tuna can help resolve the signs in short order.

To avoid this from happening, it is important to apply any topical flea/tick product to the skin in front of the shoulder blades at the back of the neck, a location even the most flexible cat cannot reach to lick. In multiple cat households where lots of co-grooming occurs, separating housemate kitties for up to 24 hours after application to allow the product to fully dry may be advisable.

Although Frontline Plus for both dogs and cats contain the same active ingredients, there are differences in the dosage of active ingredients and inactive ingredients, so the dog products should never be shared with cats.

Frontline GOLD is approved for use in breeding, pregnant, or lactating queens, but should be used cautiously in an older cat, or a cat ailing from an acute or chronic illness. Make sure to discuss with your veterinarian if any medications your cat is on may interact with a Frontline product.

If you are ever concerned that your kitty may have developed side effects while using Frontline Plus, or any topical flea/tick medication, make sure to contact your veterinarian, the ASPCA Animal Poison Control Center (1-888-426-4435), or Pet Poison Helpline (1-855-764-7661) for further advice.

(Video) How to Apply Frontline Plus to Cats | Pet Care 2021

Using Caution With Other Flea/Tick Products

While Frontline Plus for Cats has been established as a safe product, the active ingredients may be found in other products in combination with other ingredients that are not safe for cats. This is especially the case with dog products like K9 Advtantix II which contains permethrin, which is extremely toxic to cats.

Fortunately, these products are now required to include a warning against use in cats. But just to be safe, when selecting a flea/tick product for your kitty, always make sure the product includes a picture of a cat and indicates the product is specifically for cats.

It is also always advisable if you have a pup and kitty who like to hang out together or groom each other, to separate them for 24 hours after applying a topical product to your dog, especially if the product contains permethrin.

If you have any concerns for potential toxicity, even if you think your kitty might have just licked some Frontline off her fur and is having a bitter taste reaction, it is always best to contact your veterinarian, or the ASPCA Animal Poison Control Center for further advice.

And lastly, topical products like Frontline Plus have been known to cause skin and eye irritation in people. It is best to avoid contact with the solution during application and to wash your hands after.

Frontline Plus For Cats Dosage

Frontline Plus For Cats: Overview, Dosage & Side Effects - All About Cats (4)

Bathing your cat shortly before application may reduce its effectiveness.

Frontline Plus is typically applied every 30 days for the best protection. Protection against ticks is limited to 30 days, though protection against fleas can be reportedly for up to 6 weeks according to the manufacturer.

Always follow all instructions on the packaging for any topical product you use for your kitty. Frontline Plus vials come with a perforated tip that needs to be broken off or snipped off with scissors. It is then best applied by parting the fur and applying to the skin along the back of the neck in front of the shoulders where a kitty cannot reach to lick it off of himself.

While Frontline products are considered to be waterproof, make sure not to bathe your kitty for 24-48 hours after an application. Bathing shortly before application may also reduce its effectiveness.

If for some reason you are unsure if the product was administered correctly or whether all of it was applied, it is usually safest to not apply an additional dose.

If you have any questions about application or safety for Frontline products or any topical product, make sure to get in touch with your veterinarian.


Frontline Plus has been considered a safe and reliable flea/tick product for many years. However, with the addition of a second insect growth regulator, Frontline GOLD does have a superior kill time against fleas compared to Frontline Plus.

The ingredients in Frontline Plus are largely considered to be safe for kitties, though individual sensitivities can always occur. It’s important with any topical product to ensure it is specific for use in cats and to follow all instructions carefully.

Topical products like Frontline can all have different combinations of ingredients targeting different parasites that can sometimes be confusing. Make sure to clarify any questions you have about the best product for your kitty by having a chat with your vet.

Frequently Asked Questions

How Long Does It Take for Frontline Plus to Work on Cats?

According to the manufacturer, Frontline can start to kill fleas within 4 hours and can kill 100% of fleas on a pet within 12-18 hours. It is important to remember however that when first applied, it can take up to 24 hours for Frontline to be fully effective.

While Frontline Plus kills ticks, it can take up to 48 hours for them to be killed. According to the product label, mosquitoes are killed within 24 hours for up to 14 days and within 48 hours for up to 28 days.

What is the difference between Frontline and Frontline Plus for Cats?

The original Frontline product contained only fipronil, which kills only adult fleas and ticks. Frontline Plus contains the additional insect growth regulator (S)-methoprene, which targets fleas eggs and larvae as well.

Around the year 2000, Frontline Plus was released and the original Frontline started to be phased out. Frontline GOLD was released just a couple of years ago. Currently only Frontline Plus and Frontline GOLD are widely available.

Is Frontline Plus OK for Cats?

Yes, but only the cat-specific product should be used. Although both the cat and dog products contain the same active ingredients, the dosages are different, especially for larger dogs, so the dog products should never be shared with cats.

How Often Should Frontline Plus Be Applied to Cats?

Protection against fleas can be for up to 6 weeks according to the manufacturer. However, the manufacturer does recommend that if there is a high risk of flea infestation or if a cat is known to develop flea allergy dermatitis, that application every 4 weeks may be needed for the best flea prevention.

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Protection against ticks, lice, and mosquitoes is limited to 30 days. Therefore, for the most comprehensive coverage, application every 30 days is best.

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