Flea Control For Cats – Frontline


What is Frontline?

Frontline is a liquid medication that is applied to the skin of both dogs and cats to kill fleas and other parasites. Frontline is manufactured by Merial Animal Health and contains the active ingredient, fipronil. Frontline is available in a number of preparations: Frontline spot on and Frontline Combo spot on, which has an action on fleas in the environment as well as on your pet, and Frontline Spray These come in several sizes so that your pet can be accurately dosed. Frontline Spot on is not a prescription drug which means you do not need to get it from a vet, it can be obtained without a prescription from chemists or online. Frontline Combo and Frontline Spray however are POM-V medications, meaning you can only obtain them from a vet or with a prescription from a vet.

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What is Frontline used for?

Frontline spot on is used to treat a variety of parasites in both dogs and cats. It is used to prevent and treat infestations of fleas (Ctenocephalides spp.) and can also be used as part of a management regime for flea allergic dermatitis (F.A.D.) in both species. Frontline will also treat and prevent ticks (Rhipicephalus spp, Dermacentor spp and Ixodes spp). In cats, Frontline will treat biting lice in dogs and cats although the species of louse varies – Felicola subrostratus in cats and Trichodectes canis in dogs.

Frontline Combo spot on contains S-methoprene as well as the fipronil so as well as all the above indications, Frontline Combo will also stop the development of eggs, larvae and pupae which reduces the flea population in the environment as well as treating the adult fleas on your pet.

Frontline Spray will again treat the fleas, ticks and lice mentioned above but can also aid in the treatment of infestations of mites such as Harvest mites (Neotrombicula autumnalis), Sarcoptic mange and Cheyletiella.

Frontline Tips

·      Frontline is used to control fleas, ticks and lice on your pet

·      Frontline should only be used topically

·      The size of Frontline needed will depend on your pet’s weight so weigh regularly

·      If you suspect any side effects from Frontline then contact your vet for advice

·      If you’re pet accidentally receives an overdose of Frontline, call the vet for advice

·      Store Frontline in a cool place, <30oC as it is flammable

·      Frontline should be kept out of the reach of children

·      All cats and dogs in the household should be treated with Frontline

·      Frontline is available as a spot on or a spray formulation

Side Effects

·      If you suspect any side effects from Frontline then contact your vet for advice

·      DO NOT use Frontline in rabbits as it may be fatal

·      Frontline spot on should not be used in animals under 8 weeks of age

·      Frontline should not be used in cats under 1kg in weight and dogs under 2kg

·      There may be mild and temporary skin irritation at the site of application

·      Frontline can cause generalised itching over the whole body

·      If your pet licks the Frontline, you may see hypersalivation and vomiting

·      Frontline may occasionally cause mild and reversible neurological signs

·      Frontline can be dangerous to fish so don’t let it enter watercourses

 Dosage and Administration

·      Frontline is applied directly to the skin, either as a spot on or a spray

·      Frontline should not be applied to broken or damaged skin

·      The minimum time between Frontline applications should be 4 weeks

·      The whole spot on pipette should be applied to the back of the neck

·      Do not apply Frontline to wet hair

·      Do not bath animals or let them swim for 2 days after application

·      Keep animals away from flames for 30 minutes after Frontline application or until the hair is dry as Frontline is flammable

·      Do not enclose animals, e.g. in a carrier, until the Frontline is dry

·      Frontline comes in several sizes to ensure an accurate dose is given to pets

·      Gloves should be worm when applying the Frontline spray

Further Information about Frontline

Frontline is a liquid medication which contains the active ingredient fipronil, an insecticide, which is used to treat and prevent fleas, ticks and lice in dogs and cats. Frontline is manufactured by Merial Animal Health and comes in three different formulations.

Frontline spot on is applied to the skin on the back of the neck, monthly to control fleas, lice and ticks. Frontline distributes over the whole body within 24 hours but absorption through your pet’s skin is minimal.

Fipronil interferes with the nervous system of the insects by blocking receptors of the neurotransmitter GABA. This causes the fleas to be killed within 24 hours of landing on the animal. It does the same with ticks so although Frontline doesn’t stop them attaching, they will be killed with 24 hours which minimised the chance of them spreading disease. Absorption of Frontline through the skin of your pet is negligible. Frontline Spray contains the same active ingredient, fipronil and also treats fleas, lice and ticks as well as helping to control some mites such as Sarcoptes, Cheyletiella and harvest mites.

Frontline Combo spot on is also applied to the skin on the back of the neck monthly and also contains fipronil so will treat the same parasites as normal Frontline spot on, including adult fleas. Frontline Combo has the added benefit of treating flea infestations in the environment. It contains an extra ingredient, S-methoprene which is from a class of drugs called ‘insect growth regulators’ (IGR’s). This will stop the development of eggs, larvae and pupae into the adult flea. Frontline Combo achieves this either by directly penetrating the eggs or by being absorbed through the cuticle of the flea.

Frontline spot on preparations should not be used in animals under 8 weeks of age, cats less than 1kg in weight or dogs less than 2kg in weight. Frontline spray however can be used in puppies and kittens from 2 days of age. Frontline is safe for use in pregnant and lactating animals. Frontline may cause local skin irritation at the site of application but this is usually mild and temporary. If your pet licks the Frontline they may drool excessively and vomit.

Frontline is flammable so pets should be kept away from naked flames for 30 minutes and they should not be placed in enclosed spaces, for example carriers, until the hair is dry. You should not bath your pet or let them swim for2 days after applying Frontline as it may reduce the efficacy and Frontline should not be allowed to contaminate water courses as it is dangerous for aquatic creatures.

Further information on dosage and administration of Frontline

Frontline and Frontline Combo spot on preparations are applied directly to the skin on the back of the neck, at the base of the skull, where your pet cannot reach to lick them off. Hold the pipette upright so all the liquid is in the bottom half, tap if needed. Then snap off the top of the pipette along the scored line. Part the hair on the back of the neck and apply the entire contents in two locations.                                                                                                             

The sizes of Frontline spot on that your pet will need depends on your pet’s weight. There is one size of pipette for cats which contains 0.5ml of Frontline liquid, equating to 50mg of fipronil. For dogs, the dose varies more depending on weight and are summarised in the table below. These doses will deliver between 7.5mg-15mg of fipronil per kilo of bodyweight.

Weight of dog (kg)

Frontline (10% fipronil)

Package Colour














2 x 2.68ml

2 x PINK

Frontline Combo

Frontline Combo also comes in a variety of sizes and is distinct from normal Frontline spot on due to its GREEN packaging. The cat pipette again contains 0.5ml liquid equating to 50ml fipronil but in addition it also contains 60mg of S-methoprene. The table below summarises the doses required by various sized dogs. These doses give a minimum dose of 6.7mg/kg fipronil and 6mg/kg of S-methoprene.

Weight of dog (kg)

Size of Frontline Combo needed

Fipronil (mg)

S-methoprene (mg)


S     (0.67ml)




M   (1.34ml)




L     (2.68ml)




XL   (4.02ml)




Frontline Spray comes with a pump attached and is sprayed directly onto the hair coat from a distance of 10-20cm away, all over the animal. To apply Frontline Spray to the face, it is better to spray the Frontline into a gloved hand and then apply to the face, avoiding the eyes and mouth. Spray against the lay of the hair coat and then ruffle the hair so that the liquid penetrates right down to the skin.

Frontline Spray contains a 0.25% solution of fipronil. You need to apply 3-6ml of the solution per kilogram (kg) of your pet’s bodyweight.

The 100ml bottle delivers 0.5ml per spray meaning that you need 6-12 pumps of the spray per kg bodyweight. This means that a 100ml bottle of Frontline spray contains approximately 8 treatments for an average sized, short haired cat of about 4kg.

The 250ml and 500ml bottles have a different pump attached and deliver 1.5ml per spray. This means that you need 2-4 pumps of the spray per kg of your pet’s bodyweight. A 250ml bottle of Frontline Spray contains around 4 treatments for a 20kg short haired dog and a 500ml bottle of Frontline contains 8 treatments for the same dog. This will vary depending on the weight of your pet and if your dog is long haired then you will need to use the upper end of the dose range to make sure that the Frontline penetrates right down to the skin.

Frequently asked questions

Q. What is Frontline?                                                                                                                                                

A. Frontline is a liquid medication to treat fleas and other parasites which comes as a spot on treatment to be applied to the skin on the back of the neck or as a spray to be applied to the coat.

Q. What parasites does Frontline treat?                                                                                                             

A. Frontline treats and prevents flea infestations, ticks and biting lice. Frontline spray also helps treat mites such as Sarcoptes and Harvest mites.

Q. I have seen a tick on my dog, does this mean the Frontline is not working?                                           

A. No, Frontline will not stop the ticks attaching but it will kill them in 24-48 hours. They will then drop off or be easy to remove.

Q. I have seen fleas on one of my cats and I have two others. Will they all be affected?         

A. Most likely, yes. Fleas will transmit from one animal to another so all “in contact” animals in the house, both dogs and cats, should be treated.

Q. I last applied Frontline 2 weeks ago but can still see fleas. Should I apply another dose? 

A. No. The minimum time between dosing should be 4 weeks. Frontline should kill the fleas within 24 hours of them landing on your pet but if you think the problem is persisting, call your vet for advice.

Q. My cats have had fleas and I think they are now living in their bedding. Will Frontline help with this?                                                                                                                                                                

A. Normal Frontline only kills the adult fleas on the animal but Frontline Combo will treat fleas in the environment by stopping eggs and larvae becoming adults.

Q. My dog has just chewed a pipette of Frontline, what should I do?                                                              

A. You are likely to see excessive salivation and vomiting. If these symptoms are severe or prolonged then call the vet for advice.

Q. Am I likely to see any side effects after applying Frontline?                                                                         

A. Frontline can have side effects, the most common being mild skin irritation at the site of application but this is usually transient. Occasionally generalised itching and neurological signs can be seen.

Q. I applied a pipette of Frontline this morning and my husband applied another this afternoon. Will this cause a problem?                                                                                                               

A. Frontline has been tested at several times the recommended dose and appears to be safe but if you see any side effects then call the vet.

Q. Can I buy Frontline from an online pharmacy?                                                                                                     

A. Yes. You can buy Frontline spot on without a prescription but Frontline Combo and Frontline Spray are prescription only medication so you will need a prescription from your vet to obtain these.

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