How fast does NexGard® (afoxolaner) Chewables kill fleas?

In a well-controlled laboratory study, NexGard® began to kill fleas four hours after initial administration and demonstrated >99% effectiveness at eight hours.4

What does NexGard® kill?

NexGard® chews have been carefully designed to quickly kill fleas and ticks for a full month, killing fleas before they have a chance to lay eggs and black-legged ticks before they transmit Lyme infections. 

Why am I still seeing fleas on my dog after using NexGard®?

Adult fleas - the ones that you see on an infested pet - make up only ~5% of the total flea population. The developing stages (flea eggs, larvae and pupae) make up the other 95%. These developing stages can be found anywhere an infested animal spends time Commonly infested animals, which spread flea eggs throughout their surroundings, include untreated pets, feral cats, opossums, coyotes, etc.5 You are likely seeing NEW fleas on your pet, which are jumping on your dog as it moves through infested areas. These fleas will be killed quickly by NexGard® before they can reproduce. Depending on the severity of an already existing infestation, you may continue to see new fleas jumping on your pet for three months or more (depending on environmental conditions). TO prevent new infestations, continue to give NexGard® MONTHLY throughout the year. 

Does NexGard® need to be used even if I have an "indoor dog"?

Yes - fleas are opportunists. Even if your dog only goes outside to do their business, they're at risk of infestations from fleas & ticks. Fleas can even "hitchhike" into a home on people, and then jump to infest dogs. An infested pet will spread flea eggs throughout the house, which can survive in your carpet or the crannies of your wood floors and then mature to infest other animals in your home. 

How long does a dose of NexGard® last & how often should I treat my dog?

Each NexGard® Chew protects your dog for one full month, It is important to ensure that your dog receives one Nexgard® Chew each month to keep your dog protected all year long. 


NexGard® (afoxolaner) is for use in dogs only. The most frequently reported adverse reactions include vomiting, itching, lethargy, diarrhea, and lack of appetite. The safe use of NexGard in pregnant, breeding, or lactating dogs has not been evaluated. Use with caution in dogs with a history of seizures or neurologic disorders. For more information, contact your veterinarian, visit or click here for full prescribing information.

HEARTGARD® Plus (ivermectin/pyrantel) is well tolerated. All dogs should be tested for heartworm infection before starting a preventive program. Following the use of HEARTGARD Plus, digestive and neurological side effects have rarely been reported. For more information, click here for full prescribing information or visit

1 Data on file at Boehringer Ingelheim.

2 Data on file at Boehringer Ingelheim.

3 Data on file at Boehringer Ingelheim.


Dryden M. Biology of fleas of dogs and cats. Compend Contin Educ Vet. 1993(4):569-579

Data on file at Boehringer Ingelheim.


NexGard® is a registered trademark and FRONTLINE VET LABS™ is a trademark of the Boehringer Ingelheim Group. HEARTGARD® and the Dog & Hand logo® are registered trademarks of Boehringer Ingelheim Health USA Inc. All other trademarks are property of their respective owners. ©2022 Boehringer Ingelheim Animal Health USA Inc., Duluth, GA. All rights reserved. US-PET-0936-2021.


NexGard is the flea and tick protection recommended by vets. From the makers of FRONTLINE Plus, the # 1 choice of veterinarians, now comes the first flea and tick killer in a beef-flavored chew. In a tasty, bite-sized chewable, NexGard brand kills adult fleas before they lay eggs, and kills several dangerous ticks! With a variety of sizes, you can choose the perfect NexGard chewable that's right for your furry family and set the worry aside. Plus, they're brought to you by Boehringer Ingelheim, a company proud to be passionate about animal health.