Apple Cider Vinegar

Apple cider vinegar, usually shortened to ACV, is made by fermenting apple juice twice: yeast converts the sugar to alcohol, then acetic acid bacteria convert the alcohol to acetic acid. That acid is the active ingredient and the reason vinegar does anything at all. Finished ACV sits at a pH of roughly 3 to 5, and beyond trace potassium it contains almost no vitamins or minerals of consequence.

This is a topic where we are going to be unusually blunt, because the sources you will find disagree sharply and most pages pick a side without telling you there is one.

The Honest State of the Evidence

Veterinary-led sources tend to say there is no established health benefit for dogs and that the acidity can cause harm, particularly when ACV is used undiluted or in the ears. Natural-health publications treat it as a broadly useful household remedy for itchy skin, insects and gut health. Both positions contain something true.

What holds up: acetic acid is genuinely antibacterial and mildly antifungal, so diluted ACV is a real disinfectant and a reasonable post-bath rinse. What does not hold up: that it cures yeast infections, kills fleas, or corrects an animal's pH. There are no controlled canine trials on any of it. Most of the internal claims are extrapolated from small human and rodent studies on blood sugar and cholesterol, which is thin ground for dosing your dog.

The pH claim deserves a specific mention because it is repeated so confidently. The idea that most dogs are "too alkaline" and that vinegar rebalances them traces back to human blood-type diet theories and urine pH strip testing. It has no support in veterinary physiology. Mammals regulate blood pH within a very narrow range through the lungs and kidneys, and a spoonful of vinegar does not move it.

The Blood Sugar, Heart and Weight Claims

Several ranking pages list blood sugar control, lower cholesterol, weight loss and even brain protection as benefits for dogs. Every one of those comes from human or rodent studies. None has been tested in dogs. The blood sugar effect is the one to take seriously, and in the opposite direction: if vinegar can nudge glucose after a meal, that is a risk for a diabetic dog on a fixed insulin dose, not a treatment. Diabetic dogs need their vet, not an experiment.

Two Things You Should Never Do

• Never put ACV in your dog's ears. This is the most common piece of bad advice in this category. Acid in an ear canal causes drying and inflammation, can worsen an existing infection, and if the eardrum is already compromised it can cause real damage. Ear infections need a veterinary diagnosis, because the treatment differs depending on whether it is bacterial, yeast, or driven by allergies or a foreign body. Redness, discharge, odour or head-shaking is an appointment, not a home remedy.

• Never give it undiluted. Neat vinegar on the tongue or in the stomach is an acid insult. It causes mouth and oesophageal irritation, vomiting, and in severe cases has been associated with gastric ulceration. It also stings badly on any open or raw skin.

How Much to Give

Use · Amount

• Dog, oral, up to 15 lbs — 1 teaspoon daily in food or water

• Dog, oral, 16 to 35 lbs — 2 teaspoons daily

• Dog, oral, 36 to 85 lbs — 1 tablespoon daily

• Dog, oral, over 85 lbs — Up to 1.5 tablespoons daily

• Topical rinse or spray — Equal parts ACV and water

• Post-bath coat rinse — 1 cup ACV to 2 to 4 cups water

• Horse, in feed — 1/4 to 1/2 cup daily

• Cats — Generally not recommended orally

Start below those figures. If you are adding it to a water bowl, use a small amount in a full bowl and check that your dog still drinks readily — many will not, and a dog avoiding its water is a worse outcome than whatever you were hoping to achieve.

How to Use It Topically

Do a spot test first. Apply the diluted solution to a small patch, wait twenty-four hours, and look for redness or increased itching before going near the whole animal. Then mix equal parts ACV and water in a spray bottle, or make a rinse to pour over the coat after a bath and massage in. You can let it air dry. Diluted ACV also does a genuinely good job of removing soap residue and leaving the coat glossy.

Keep it away from eyes, and off any wound that is open, raw or weeping. If it stings, you are using it somewhere it should not be.

Paw Soaks

For a dog who licks and chews at its feet after walks, a diluted soak is a practical use. Mix equal parts ACV and water in a shallow basin, stand each foot in it for a few minutes, then dry thoroughly between the toes — damp fur between the pads is exactly where yeast thrives. Skip it on cracked, bleeding or raw pads, and if the licking keeps going or the feet smell musty, that points to allergies or infection needing a diagnosis.

Fleas and Yeast: Managing Expectations

Fleas. ACV does not kill fleas. The smell may make an animal slightly less attractive to them, which is worth something on a walk in bug season but is nowhere near a flea control programme. An actual infestation needs a proper preventative from your vet, plus treating the environment. Relying on vinegar while a flea burden builds leads to flea allergy dermatitis and, in small or young animals, anaemia.

Yeast. Yeast overgrowth on skin and in ears is almost always secondary to something else, usually allergic skin disease that has damaged the skin barrier. Acidifying the surface does not address the cause, and there is no evidence ACV clears a yeast infection. If your dog has greasy, musty-smelling skin or chronically inflamed paws, the useful path is a diagnosis. Our piece on allergies in dogs covers how that workup usually goes.

Urinary Tract Infections and Bladder Stones

ACV is widely recommended to “prevent UTIs” and even “dissolve bladder stones” by acidifying the urine. This is the claim we would push back on hardest, because it can backfire.

Bladder stones come in different types, and the two most common, according to VCA, are struvite and calcium oxalate. They behave oppositely. Veterinary internists writing in Today’s Veterinary Practice note that calcium oxalate crystals are less soluble in acidic urine, that the target urine pH for these dogs is 6.5 to 7.5, and that calcium oxalate stones cannot be dissolved at all — they have to be physically removed. Acidifying the urine of a dog who makes that kind of stone moves things the wrong way.

• A UTI needs a urine test, and usually antibiotics chosen from it. Vinegar does not replace that.

• Stones need identifying by X-ray, ultrasound or stone analysis before anyone decides on a diet.

• See your vet the same day for straining, blood in the urine or frequent small wees. A dog straining and producing nothing is an emergency.

Dogs, Cats and Horses

Cats are the species to leave out of this. They are far more sensitive to strong smells, they groom obsessively so anything topical gets swallowed, and their livers handle some compounds differently from dogs, which we cover in cat safety. We would not give ACV to a cat orally.

Horses are where ACV has its most interesting application. It is fed routinely at a quarter to half a cup daily, and unlike the dog claims there is a specific line of research behind it: feeding vinegar lowers colonic pH, and lower colonic pH has been studied in relation to reduced enterolith formation in horses, particularly those on alfalfa-heavy diets in regions where enteroliths are common. It is also used topically on thrush and for general hoof hygiene, and as a feed and water flavouring. That last use is genuinely practical for both horses and dogs — an animal accustomed to a faint vinegar taste in its water will accept strange water away from home, which matters at a show or on a long trip. Our piece on trailering stress covers the other half of that problem.

Horses: The Ulcer Caution and the Fly Spray Question

Gastric ulcers. Stable folklore says vinegar settles a sour stomach. Equine nutrition sources are much more cautious. Mad Barn warns that excessive use may irritate the gut, and the feed company Sano points out that acid in the upper stomach can aggravate existing ulcers or gastritis. The upper, non-glandular part of the horse’s stomach has little protection against acid. For a horse with diagnosed or suspected ulcers — girthy, off feed, losing condition — leave the vinegar out and talk to your vet.

Fly spray. ACV is a staple of homemade fly sprays and many commercial ones. There is no good evidence that it repels flies, and Sano notes that acetic acid may actually attract some flying insects. If flies are a real problem, use a proven equine repellent and manage the environment.

“De-acidifying” the horse has the same problem as the dog pH claim: vinegar is neutralised in the gut long before it could change anything in the body’s tissues.

What to Look For When Buying

Choose raw, unfiltered, unpasteurised, organic apple cider vinegar, ideally in a glass bottle. The cloudy sediment is "the mother", a cellulose and bacterial matrix left from fermentation, and it is what distinguishes this from the clear filtered product. Pasteurisation kills the live cultures, which is the one aspect of the raw-versus-processed argument that has a straightforward mechanism behind it. Avoid ACV tablets and gummies made for humans, which frequently contain sweeteners.

Side Effects and Cautions

• Mouth, throat and stomach irritation from insufficient dilution, up to vomiting and ulceration.

• Skin irritation and dryness topically, and worsening of already inflamed skin.

• Tooth enamel erosion with long-term oral use in sensitive animals.

• Water refusal, which is a real and underrated risk.

• Kidney disease — an added acid load is not helpful in an animal whose kidneys are already managing acid-base balance poorly.

• Diabetes — acetic acid can affect post-meal blood glucose, so a diabetic animal on insulin needs veterinary input rather than an experiment.

• Vinegar sensitivity shows up as vomiting, furious scratching or reddened skin. Stop immediately.

When to Talk to Your Veterinarian

Before using it at all in an animal with kidney disease, diabetes, or a history of gastrointestinal ulceration. And instead of using it for any ear problem, any wound that is more than superficial, any skin problem that has been going on more than a week or two, and any flea burden you can actually see. Those are all diagnosable conditions with treatments that work.

How It Fits With Hemp

They overlap in one practical spot: itchy, uncomfortable skin. ACV is a surface treatment at best, and the underlying problem is usually allergic. Hemp is used by owners for general comfort and for the restlessness and constant licking that come with an itchy dog, and our side effects piece is worth reading alongside. One practical note: a spoonful of coconut oil or a hemp seed oil serving is a far better carrier for anything you want your dog to actually swallow than vinegar is. Our serving guide has the amounts, and every batch carries a certificate of analysis.

Frequently Asked Questions

Is apple cider vinegar safe for dogs? Diluted, in small amounts, it is not toxic and most dogs tolerate it. Undiluted it is an acid and can cause real irritation. Never put it in the ears.

Does apple cider vinegar kill fleas on dogs? No. At most it is a mild repellent. An actual flea problem needs a veterinary preventative and environmental treatment.

Can I use apple cider vinegar on my dog's itchy skin? Diluted equal parts with water, as a spray or post-bath rinse, after a twenty-four hour spot test. Never on open, raw or weeping skin. If the itch persists, get a diagnosis.

Can apple cider vinegar clear a yeast infection? There is no evidence that it does. Yeast overgrowth is usually secondary to allergic skin disease, and acidifying the surface does not treat the cause.

How much apple cider vinegar can I put in my dog's water? Start with about a teaspoon in a full bowl and confirm your dog still drinks normally. If drinking drops off, stop — hydration matters more.

Can cats have apple cider vinegar? We would not give it orally. Cats are more sensitive to strong smells and groom everything off their coat, so topical use gets swallowed.

For the veterinary-side view, Chewy's education team published a vet-reviewed piece on apple cider vinegar for dogs. On the equine enterolith research, the University of California Davis veterinary school publishes material on enteroliths in horses.

Can apple cider vinegar cure my dog's UTI?

No. A urinary tract infection needs a urine test and usually antibiotics. Acidifying the urine can also make some bladder stones, particularly calcium oxalate, more likely.

Can I soak my dog's paws in apple cider vinegar?

Yes, diluted equal parts with water for a few minutes, then dried well between the toes. Not on cracked or raw pads, and see your vet if the licking continues.

Is apple cider vinegar good for horses with ulcers?

We would not use it. Acid can aggravate the unprotected upper part of the horse’s stomach. Horses with ulcer signs need a vet and, usually, gastroscopy.

Does apple cider vinegar keep flies off horses?

There is no good evidence it does, and acetic acid may even attract some insects. Use a proven fly repellent.