I've mixed nutritional yeast or brewer's yeast with my cat's dry food for 3 years and he is almost always completely free of fleas etc.

When pet sitting my friends' dog, she had ticks and I suggested this to them. In researching it now I see the difference between brewer's and nutritional yeast seems to be chromium, which one site mentions is good for skin. Another site mentioned some toxicity with chromium.

Does anyone have true data. on this?

I may have unknowingly switched between both over years but the effects were still good on my cat.


4 Answers 4


I searched extensively for a reliable reference on yeast as an effective flea treatment. I found multiple mentions of the treatment. Some mention it 'might' be an effect treatment. All mention studies that say there was not evidence to support the treatment, some casually mention studies supporting the treatment.

I found no indicators that yeast might be harmful to a cat or dog.

I was not able to locate any actual published studies that were not behind firewalls. The few Google snip-its I got, did not hint at any studies that showed benefit for flea control using any yeast.

In summary, you can give either yeast. Neither is likely to cause harm to your dog or cat, but there is little to no solid evidence supporting it as an effective flea treatment.

Related question Can dish soap really be used to kill ticks and fleas?

  • I found a study on PubMed with a free abstract that found no benefit from yeast for flea treatment in dogs. See PMID 6885593.
    – augurar
    Sep 1, 2014 at 4:59

When I was younger my older brother worked security for a college and the head of the department was involved with many local police departments and the DEA. My brother had a Rottweiler that the college offered to go through the DEA training, to help locate drugs on campus. This dog went through and passed with flying colors to find drugs and locate missing people.

While in the program, the trainers recommended using Brewers Yeast pills to prevent fleas and ticks (since he would be searching for missing persons in wooded areas and also doing a lot of agility training outside). He started using the pills, and so I also started my Rottweiler on them (1 pill per day mixed in with food). I now have a Boxer and a Pitbull who I also treat the same way; never once have any of these dogs had a flea on them!

They ultimately produce a smell/taste that the insects do not find attractive. Other benefits are that their coats are shinier, less shedding, and less skin irritations. I highly recommend using Brewer's Yeast for dogs (I also heard it works with cats).

I purchase my pills at either “The Vitamin Shoppe” or “GNC”. I currently am using the Vitamin Shoppe brand, cost is about $10.00 for a bottle of 500 pills.

Also, the nutritional values are:

- dairy free, soy free, and nut free.
- 10 calories per pill.
- 1.2g Carbs.
- .07 fiber.
- 2g protein.
- 470mcg of Vit B1 and 160mcg of B2 (both are very good health benefits for dogs).
- 1170mcg of Niacin.
- 3900mg of Brewers Yeast.
- No Garlic is included.

I highly recommend these pills to everyone I know with pets and those who have used them say the same, they really work to repel insects, and the bonus of the health benefits. To anyone who reads this, I suggest you give them a try and see the benefits for yourself.


I have two goldens and I give them 1 tsp of nutritional yeast in their breakfast four times a week - all year long. No fleas, yes in August too. I have not found ticks on them until recently, but the ticks do NOT imbed or attached to them. I paid $8 for the bag of organic nutritional yeast in March (7 mo ago) and still have 1/3 left. (The nutritional yeast seems to have gotten the job done where as Brewers yeast in the past didn't get the same result with me.)


I had five doggies and five cats. I gave them all nutritional yeast flakes throughout the warm months. Not a one got fleas or ticks. I walked them in nature. This included the mountains and the high desert. We did not get flea bites, either. So, anecdotally, yes, I support that nutritional yeast flakes are very helpful as natural insect repellants.

Nutritional yeast flakes are also tasty on popcorn and as a dip for chips and veggies.

  • Dee, if you see this, how much nutritional yeast did you give your cats? I'm looking for a safe dose for 5 week old kittens and their momma.
    – Jen M.
    Oct 28, 2023 at 19:55

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