Frontline Combo

Frontline Combo Spot-On


Liquid Spot-on

Active ingredient

Fipronil, (S)-methoprene

Frequency of use

Every 4 weeks

Minimum age/weight

8 weeks (2kg)


Fleas (adults), fleas (immature), ticks, biting lice

What is Frontline Combo?

Frontline Combo is a topical medication for dogs and cats that helps protect them from a range of external parasites, primarily:


  • It kills adult fleas rapidly: It eliminates them within 24-48 hours of application, offering immediate relief from itching and discomfort.
  • It prevents future infestations: It stops flea eggs from hatching and larvae from developing, effectively breaking the flea breeding cycle for long-lasting protection. This typically lasts for up to 8 weeks in dogs and 4 weeks in cats.


  • It kills attached ticks within 24-48 hours: It helps prevent transmission of tick-borne diseases like Lyme disease.
  • It offers some protection against future tick infestations and provides continued protection for up to 4 weeks in both dogs and cats.

Additionally, some versions of Frontline Combo also offer protection against:

  • Biting lice: Effective in eliminating and preventing infestations of these lice in both dogs and cats.

What does Frontline Combo do?

Combats existing flea and tick infestations:

  • Rapidly eliminates adult fleas within 24-48 hours: Fipronil, one of two active ingredients, acts on their nervous system, causing paralysis and death. This provides immediate relief from the discomfort and scratching caused by these biting pests.
  • Kills attached ticks within 24-48 hours: This helps prevent your pet from contracting potentially serious tick-borne diseases like Lyme disease.

Prevents future flea outbreaks:

  • Stops flea eggs from hatching and larvae from developing: S-methoprene, another key ingredient, acts as an insect growth regulator. It halts the flea breeding cycle by mimicking a natural insect hormone, this stops the next generation of fleas from maturing. This provides long-lasting protection for up to 8 weeks in dogs and 4 weeks in cats.

Once applied, Frontline Combo is stored in the oil glands of your pet’s skin. This allows for it to be released slowly over a prolonged period. This ensures continuous protection against fleas and ticks, maintaining a flea-free and comfortable environment for your pet.

What is Frontline Combo for?

Frontline Combo helps control ectoparasites (parasites that live on your pet’s skin) in the following situations:

  • Flea Infestations: All adult fleas on your pet are killed. This provides instant relief for your pet. It also interrupts the growth cycle of the fleas, preventing them from maturing. This means the infestation is brought under control more rapidly than if using a product that just kills adult fleas.
  • Tick Control: Fleascreen Combo kills ticks. This means it helps to prevent the spread of tick borne diseases too.

What are the possible side effects with Frontline Combo?

Frontline Combo is generally well-tolerated, but it’s essential to be aware of potential side effects. These can include:

  • Skin reactions: These are the most common, occurring at the application site and typically resolving within a few days. They may include redness, changes in pigmentation, alopecia, itching, greasiness and clumping of hair.
  • Excessive salivation: This can occur if your pet licks the product at the application site immediately after application. It’s usually brief and harmless.
  • Vomiting: This is usually mild and short-lived.
  • Nervous system signs: These are rarely seen and may include, increased sensitivity to touch, depression, lethargy, tremors and ataxia (incoordination).

Other Potential Side Effects:

  • Eye irritation: Avoid contact of the product with your pet’s eyes.
  • Allergic reactions: While rare, allergic reactions to Frontline Combo can occur. Signs may include, hives, difficulty breathing and facial swelling.

Important things to remember:

  • The risk of side effects increases with if an overdose has been given. Ensure to use the correct dosage recommended by your vet based on your pet’s weight and species.
  • Certain individuals may be more prone to side effects.
  • Stop using Frontline Combo and consult your vet immediately if you notice any severe or persistent side effects in your pet.

How to give Frontline Combo safely

Using Frontline Combo safely on your pet requires using proper application techniques and taking precautions to ensure your pet’s well-being. Here’s a step-by-step guide to help you administer it safely:

Before application:

  • Consult your vet: They will determine the appropriate dosage based on your pet’s weight and species. This is an opportunity to discuss your pet’s health, any existing conditions, and whether Frontline Combo is the right choice for them.
  • Read the product instructions carefully: Familiarize yourself with the contents, dosage guidance, and application method to avoid errors.
  • Gather supplies: You’ll need the Frontline Combo tube, gloves (optional), and a towel (optional).

Application process:

  • The product should be applied directly to the back of your pet’s neck between the shoulder blades. This location is chosen to prevent your pet from licking the product off their skin.
  • Part the fur: Gently part the fur to reveal the skin at the application site.
  • Hold the tube upright: Point the nozzle away from your pet and yourself.
  • Apply the solution: Squeeze the tube gently, depositing the required amount of solution directly onto the exposed skin. Avoid applying to broken skin or wounds.
  • Do not massage: Allow the solution to spread naturally on your pet’s skin.
  • Discard the used tube safely.

After application:

  • Wash your hands thoroughly.
  • Monitor your pet: Watch out for any clinical signs of side effects. Contact your vet if you notice any concerning signs.
  • Keep your pet away from water for 24 hours: This allows the solution to dry and become effective.
  • Do not bathe your pet for 2 days: this may remove some of the product.
  • Prevent licking: Use an Elizabethan collar (cone) if your pet tends to lick or chew at the application site.

Additional safety tips:

  • The product should not be used on pets less than 8 weeks old and/or weighing less than 2 kg.
  • Do not use it on sick animals.
  • Do not use in rabbits, as adverse drug reactions, even mortality, could occur.
  • Store Frontline Combo in a cool, dry place, out of reach of children and pets.
  • Do not overdose. Stick to the recommended dosage prescribed by your veterinarian.
  • Do not apply Frontline Combo more frequently than recommended. Overuse can be harmful to your pet.

Frontline Combo FAQs

What is the difference between Frontline and Frontline Combo?

Frontline and Frontline Combo are both topical flea and tick treatments for dogs and cats, but they have some key differences:


  • Frontline: Primarily kills adult fleas and ticks, offering quick relief from biting but not preventing future infestations.
  • Frontline Combo: Combines the same flea and tick killing action as Frontline with s-methoprene, an insect growth regulator. This breaks the flea breeding cycle by preventing eggs from hatching and larvae from maturing, offering long-term flea prevention for up to 8 weeks in dogs and 4 weeks in cats.


  • Frontline: Targets adult fleas and ticks only.
  • Frontline Combo: Targets adult fleas and ticks. Prevents flea eggs from hatching and larvae from maturing.

What does Frontline Combo treat?

Frontline Combo primarily treats and prevents infestations of fleas and ticks. Adult fleas are eliminated in 24-48 hours. Further flea infestations are prevented as the flea breeding cycle is disrupted. Eggs are prevented from hatching and larvae are prevented from developing so no new fleas appear. Ticks are killed within 24-48 hours.

Is Frontline Combo prescription only?

Yes, Frontline Combo is a prescription-only medicine. This means that you cannot legally purchase it without a valid veterinary prescription. This is because Frontline Combo contains fipronil and s-methoprene, which are classified as veterinary medicines under the Veterinary Medicines Regulations 2013.

How long does it take for Frontline Combo to work?

Frontline Combo’s timeframe for effectiveness depends on the specific target and desired outcome:

Killing Adult Fleas and Ticks:

  • Fast action: Fipronil, the primary insecticide, starts working rapidly. It begins affecting these parasites within 24 hours, and most adult fleas and ticks will be dead within 24-48 hours. This means you can expect relief from itching and scratching relatively quickly.

Preventing Future Flea Infestations:

  • Gradual effect: S-methoprene, the insect growth regulator, takes a bit longer to show its full impact. It acts primarily on flea eggs and larvae, preventing them from developing into biting adults. While it starts within 24-48 hours, the full impact takes around 6-8 weeks. This is because existing eggs and larvae complete their life cycle before being effectively stopped by the medication.


  • Immediate relief: Expect relief from existing flea and tick problems within a day or two.
  • Complete protection: Full protection against future flea infestations takes around 6-8 weeks with consistent use every 4 weeks.

Frontline Combo Datasheet

All drugs have a manufacturer’s datasheet, which gives information about the drug’s use and possible side effects. There is usually one in your Frontline Combo box, but if you have lost it you can click on the button below to be taken on an online version.

Struggling with a flea problem?

No pet should have to suffer with fleas. But it can be hard to beat them. In this FREE resource, our vets explain why flea treatments fail and explain how to choose a flea treatment that suits your pet!

Please note that the information contained herein is provided for informational purposes only. Although it has been written by a vet, we cannot consider the individual nature of your pet’s problems so it does not constitute veterinary advice. If you have questions about your pet’s medication or their health you should contact a vet, who will be able to help.