A highly effective innovation in flea treatment

How it works in killing fleas is the real innovation

Activyl is a unique spot-on flea control treatment featuring indoxacarb and a mode of action that uses enzymes inside the flea to activate serious flea-killing power. Both pets and people want a flea treatment that's really effective at killing fleas and preventing infestation, but how it works matters, especially regarding the impact to your pet and home.

Activyl can be purchased at your veterinary clinic. This ensures that your furry family member gets the best care possible. It's also quick-drying, fragrance-free, waterproof and remains effective even after bathing.1,2

How does Activyl break the flea life cycle?

Unlike some flea treatments, Activyl doesn't just kill adult fleas, it also stops flea eggs and larvae from developing.1,3 Breaking the flea life cycle is important, so your pet is not re-infested by new fleas developing from flea eggs and larvae in your own home environment.

Activyl for Dogs is the flea treatment just for dogs and Activyl for Cats is the flea treatment just for cats. Both products kill adult fleas and also break the flea life cycle,1,3 so you're much more likely to solve your pet's problem for good.

How it works1

Step 1

Step 1: Application

Activyl spreads through your pet's skin and coat.

Step 2

Step 2: Contact and Ingestion

When a flea lands, it takes up Activyl (no bite required).

Step 3

Step 3: Activation

Enzymes inside the flea change Activyl into its fully active form.

Step 4

Step 4: Flea-Free

The flea is soon unable to feed, becomes paralyzed and dies.

PLEASE NOTE: At the beginning of Phase 4, fleas become disoriented and move in the coat of your pet, which makes them more visible to you. These fleas stop feeding, followed closely by paralysis and death.

Treat the Cause of Flea Allergy Dermatitis (FAD)1,4

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Product Information

Brief Summary:
Please consult the full package insert for more information.5

For Dogs:
Activyl Spot-On for Dogs and Puppies is indicated for use once a month on dogs and puppies that weigh over 4 lbs and are 8 weeks of age or older.
For Cats: Activyl Spot-On for Cats and Kittens is indicated for use once a month on cats and kittens that weigh 2 lbs and are 8 weeks of age or older.

ADVERSE REACTIONS: The following adverse reactions have been reported following use at the recommended dose: salivation occasional scratching hair loss and redness of skin at the application site. These mild side effects were temporary and did not require treatment.

HOW SUPPLIED: Activyl is available in 1-packs and 6-packs of snap-open see-through applicator(s). Each applicator comes in an easy-open foil pouch. Activyl Spot-On is available in different presentations to fit all sizes of dogs and cats. The volume present in each applicator ranges from 0.51 mL to 4.62 mL for dogs. The volume present in each applicator for Cats and Kittens is either 1.03 mL or 0.51 mL, respectively.

Store in a cool, dry place inaccessible to children and pets. Flammable, Keep away from heat and open flame.

For technical assistance, call Merck Animal Health at 1-800-224-5318.


  1. Data on file at Merck Animal Health.
  2. Qureshi T, Balgburn B, Yound D, Sun F, Guerino F. Effects of water immersion and shampooing on the efficacy of an indoxacarb spot-on against cat flea (Ctenocephalides felis) infestation on dogs. Presented at the BSAVA/WSAVA/FECAVA World Congress, 12-15 April 2012, Birmingham, UK.
  3. Guerino F, Qureshi T, Hair J, Young D, Fiourie J. Indoxacarb Kills Developing Stages of Fleas in the Environment of Treated Cats. Presented at the WSAVA/FECAVA/BSAVA World Congress. 12-15 April 2012. Birmingham, UK.
  4. Fisara P, Sargent R, Flochlay-Sigognault A, Frenais R, Guerino F. Efficacy of indoxacarb spot-on in resolving clinical signs of flea allergy dermatitis in dogs cats and other field conditions. Presented at the BSAVA/WSAVA/FECAVA World Congress, 12-15 April, 2012, Birmingham, UK.
  5. Activyl® Product Insert.