http://npic.orst.edu/factsheets/fipronil.html#:~:text=%2D858%2D7378.-,How%20does%20fipronil%20work%3F,bind%20to%20insect%20nerve%20endings

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. A Frontline overdose in cats is extremely rare, but applying or ingesting too much product will likely produce many of the side effects listed above. Still, if you know that your cat has been exposed to more than the prescribed dose of fipronil and is experiencing side effects, you should take them to a veterinarian as soon as possible for evaluation.con icon Two crossed lines that form an 'X'. Not recommended for kittens younger than 8 weeks of age https://uk.frontline.com/can-i-handle-or-stroke-my-pet-after-applying-frontline-plus-frontline-tri-act-frontline-spot Comfortis is one of two oral flea control products available for cats; the other is Capstar Flea Control Tablets. Unlike Capstar, which kills fleas for only 24 hours, Comfortis protects cats against fleas for an entire month. However, Comfortis is not safe for kittens younger than 14 weeks old, while Capstar is safe for kittens as young as 4 weeks old. Dr. Ashley Bourgeois, a veterinary dermatologist at Animal Dermatology Clinic, prefers Revolution Plus, saying that its active ingredients ( selamectin and sarolaner) are very effective and well-tolerated by cats.

Thanks for your question. Before assuming the product doesn’t work, there are some things to consider. When there’s an active flea infestation and Frontline is applied to stop it, it can take 24 hours initially for the product to disseminate through the skin. 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.Bathing/shampooing/water exposure does not affect the efficacy of the product as long as it does not occur more than once a week. con icon Two crossed lines that form an 'X'. Not labeled for use in breeding, pregnant, or nursing cats Yes! You must wait 24-48 hours for the product to dry thoroughly, but you can handle your cat as usual once it does. However, you should not touch, stroke, or cuddle them prior. This is especially true for children. Wear gloves and wash your hands if your pet wants attention or you need to handle them for any reason, such as giving medication, during this time. Can Frontline Be Used on Kittens Younger Than 8 Weeks? Available without a prescription, Capstar is the only flea control product safe for kittens as young as 4 weeks and weighing at least 2 pounds. Kittens must be at least 8 weeks old and sometimes older to be treated with other topical or oral flea control products. Your pet is now treated:the treatment will naturally spread over their skin, however do not bathe your pet or let them swim for 2 days after application.