Can you use frontline plus on dogs in heat?

No, Frontline Plus should not be used on dogs in heat. The active ingredients in Frontline Plus, fipronil and (S)-methoprene, can be harmful to dogs in heat. Fipronil is a neurotoxin that can cause seizures, tremors, and other neurological problems. (S)-methoprene is an insect growth regulator that can interfere with the dog's reproductive cycle.

If you are considering using Frontline Plus on your dog, it is important to talk to your veterinarian first. Your veterinarian can help you determine if Frontline Plus is safe for your dog and can recommend other flea and tick prevention methods that are safe for dogs in heat.