Ingredients in Zodiac Spot-On Flea Treatment for Cats

Topical flea treatments are effective in combatting flea infestations.
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Fleas are more than a nuisance to a cat owner, as they can also transmit diseases to cats and humans. To combat the problematic effects of fleas, cat owners must treat both cat and the cat's environment. One effective treatment involves the application of topical remedies to the cat's skin.

“Spot On” Ingredients

Zodiac “Spot On” contains the active ingredient (S)-Methoprene. The EPA has registered Methoprene as a biochemical pesticide that does not cause adverse effects to humans. Classified as an insect growth regulator, Methoprene interferes with the fleas’ ability to develop from larvae into reproductive adults. IGR’s mimic growth hormone, and their presence prevents the flea eggs from developing and the larvae from molting. Because this ingredient acts by disrupting the life cycle of the flea, it is slow acting. Methoprene is only effective against immature fleas so it is important to combine it with a faster-acting product designed to eliminate adult fleas.

“Spot On Plus” Ingredients

Zodiac “Spot On Plus” combines the active ingredient, Methoprene, with Etofenprox. Etofenprox is a type of synthetic compound known as a pyrethroid. This ingredient effectively kills and repels not only fleas, but also ticks, lice and mosquitoes. While some pyrethroids are not safe to use on cats, Etofenprox is a safe feline ingredient. Because “Spot On Plus” combines the life-cycle disrupting Methoprene with the flea killing Etofenprox, it targets both juvenile and adult fleas. These two ingredients provide cats with a faster and wider range of protection against flea infestations.


Cat owners apply these topical flea treatments by putting the liquid on the skin between the cat’s shoulder blades. The cat’s skin absorbs the product, and additional product moves through the cat’s coat. This accomplishes whole-body flea treatment. Applications of Zodiac’s “Spot On” and “Spot On Plus” last up to one month. They are still effective if your cat gets wet or after occasional baths with a mild shampoo.


It is important to treat the cat’s environment in addition to treating the cat. Treating the environment prevents re-infestation by eliminating the fleas and flea larvae that might be lurking. Additionally, once the product dries, it is safe to allow children to pet the cat.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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