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3-PACK Felisyl® Immune System Support Granules (10.5 oz)

Regular Price: $47.58Sale Price: $27.99
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Felisyl® is a supplement that contains the amino acid L-Lysine for use in cats and kittens for conditions responsive to L-Lysine. L-Lysine is an essential amino acid, which means that your catís body needs it, but canít produce it, so this supplement is a perfect choice to provide that necessity.

L-Lysine HCL Immune System Support for Cats helps keep your cat healthy by supporting the immune system naturally so that it can function normally and produce antibodies. Felisyl L-Lysine HCL Immune System Support for Cats also helps maintain healthy tissue, supports respiratory health, and may even help with your catís vision. The L-Lysine is in a palatable poultry and fish flavored base making these granules easy to give to your cat, just sprinkle over or mix with food.

For Use In: Cats

Usage Information

Sprinkle measured amount over cat’s food and mix in. This product is intended for intermittent or supplemental feeding only.

Age of Cat Morning Evening
Under 6 months 1/2 Scoop 1/2 Scoop
Over 6 months 1 Scoop 1 Scoop


Guaranteed Analysis per (1 cc Scoop):
(All values are minimum quantities unless otherwise stated.)
Moisture (max) 1.1%
L-Lysine 78% (250 mg)
Ingredients: L-Lysine, Chicken Liver Powder, Fish By-Products, and Sugar.

Customer Reviews

DISCLAIMER: The results described on the testimonials on this site, are the individual experiences and personal opinions of those who have purchased and used the products. These testimonials are not intended to make any claims that the products can be used to diagnose, treat, mitigate, cure or prevent any disease or medical condition.
Click here to see all reviews
4.73 rating based on 15 reviews
by from 04/10/2012

My vet told me to add lysine to my cat's food. He had a herpes infection when I rescued him. The lysine is supposed to help recurrences and thus far Simon has had none.

Felisyl by with from hisI


Great product by DustyJ from elgin tx06/15/2013

Cats like the lysine powder (all 9 of them) - a first! easy to put on wet or dry food. I use a slight spray mist of water which helps the powder stay attached to the dry food and voila it is eaten without problems

Felisyl by Kazuye from Los Angeles08/17/2014

My cat caught the herpes virus while a kitten at the animal shelter. Felisyl helps her from getting so much sneezing and stuffy nose symptoms. I mix it into her food everyday and she doesn't mind it at all.

This is Great Stuff! by annetta from kansas03/29/2013

Felisyl helps the immune system of cats. My cats have frequent sneezing and it takes care of it. Likely the vet said it's probably from cat herpes. But many cats have this. Any time a respitory problem...cold or stuff like that starts...give them felisyl. It's best to not give daily unless your cat has a severe or ongoing problem. It works for my babies and it may likely make your vet trips much less needed.

great product by dustyj from austin, TX02/26/2014

I have a cat with a chronically irritated eye and she is also FIV positive. My veterinarian had suggested l-lysine to help decrease the viral load and she suggested this. I sprinkle some on a bit of wet food or spray water on her dry food and sprinkle some on it. She gets her doses twice a day - no hassle.

Felisyl recommended by my vet by Tutti from Los Angeles02/06/2013

Great product especially for those of us that have more than 1 cat because you can use it every day in their food and it strengthens their ammune system. I am on my 4th container. Entirely Pets has the best price according to my vet.

Felisyl Immune System Support by I don't have a nickname from North Carolina07/01/2013

The cats like it, Use it to help keep foster kitties healthy.

by Cat Lady03/23/2012

Have had the cats on this for years to keep down the symptoms of the kitty herpes type illness. They like the taste and it works well. Much easier to use than the paste and more economical too.

Very nice product by vj from IN12/14/2012

My cats must like the taste because they eat it up when I sprinkle it on their food!

great stuff by fostercatmom from Indianapolis, IN08/19/2012

I have volunteered with an animal shelter for over 10 years. We put lysine on the food of all the cats because it helps with the herpes virus that runs through all shelters. It doesn't cure the virus, just helps to keep it from replicating. This version is flavored and the cats like it.

good value by Tuxcats12/17/2012

There are other L-Lysine products, same ingredients, at a higher cost, on the market, and at the Vet's office. Happy with product, price, and great service.

Excellent purchase price by cati from Kansas08/07/2013

This L-Lysine HCI supplement for cats is less expensive than the vet recommended Viralys. So far, it has been just as effective to address herpes in my cats. The best part about Felisyl is that the cats actually eat it readily when mixed with canned cat food.

not just for feline herpes by mindymoon12/14/2013

I took in a very sick stray 3 years ago He had an upper respiratory infection so severe that 3 different vets weren't sure he would make it. He also tested positive for Feline HIV. Vet suggested Viralys for immune support. I've had him on Felisyl for 3 years. After months of TLC and antibiotics, he got healthy and gained weight. His coat is beautiful, eyes and ears clear. And he has stayed very healthy since. I think the Felisyl helps, so will continue it for the rest of his life. I add a scoop to his wet food once a day.

My cat liked the Viralys better by MaryAnnSanDiego from San Diego, CA07/06/2011

I had been using the Viralys powder for about a year with no problem. Just decided to try the Felisyl since it was a little cheaper. My cat backs away from ANY food I put down with the Felisyl mixed in. Eventually after complaining for a while, she will eat! I will go back to the Viralys so I won't have any food issues. Both products seem to work the same, however.

by Kazi's Mom06/07/2013

This product has done a good job keeping my kitties from having feline herpes return. It is a good immune system builder.


Questions and Answers

NASC Certified

This product has met all of the stringent quality and safety standards set by the NASC.

The NASC (National Animal Supplement Council) is a non-profit self regulatory group that set specific guidelines to which manufactures must strictly adhere.

This seal is meant to minimize risk by providing an easy way of communicating to consumers that a product and its manufacturer meet particular standards of quality, customer safety and service.

Those products that have the seal for NASC Quality and Safety standards have been strictly audited and were determined as meeting the following criteria:

  • Consistent manufacturing quality control
  • A system for evaluating complaints and adverse events
  • Clear and accurate labels compliant with codes and restrictions for all forms of labeling
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