Quercetin is a crystalline pigment with antioxidant properties found in various fruits and vegetables. It is sometimes used as a natural alternative to antihistamine drugs such as Benadryl and Zyrtec. While not yet approved by the FDA for veterinary use, it is thought to be extremely safe, with no known side effects apart from gastric upset (uncommon) when taken at moderate doses. It can be difficult to find in stores but is readily available online both with and without the addition of bromelain to aid the rate of absorption and provide additional antihistamine effects.

Which formulation is best for my dog?

Quercetin products made for humans could contain an assortment of ingredients which aren’t safe for use in dogs. For this reason it’s always best to choose a product that has been made for animal use. We recommend BioSKIN&COAT.

Recommended Dosage

There is currently little data regarding the dosage dogs. You should always ask your vet for approval before giving this supplement to your pet. Dr. Carol Jean Tillman recommends a dosage of 5 to 10 mg/lb twice daily.

Quercetin dosage chart for canine use

The chart shows the lowest end of the scale. The dosage of bromelain when given to dogs is often a little higher, around 15 mg/lb, so an accidental overdose of bromelain through quercetin supplementation is unlikely.

Example: If your dog weighs 50 lbs you would need to give them 25 to 50 mg twice a day.

How Safe Is It?

There isn’t yet much research into the safety of this supplement for use in dogs. When used at regular doses there are rarely any sides. However, abnormally high amounts could cause kidney damage and higher incidence of diarrhea and headaches. Because there is not currently information regarding the use of the supplementat during pregnancy we advise avoiding use in pregnant dogs.

Contraindications & Drug Interactions


Dogs with kidney disease may not be suitable for treatment. The vet will advise you further and suggest alternative remedies in these cases.


Bromelain may be unsuitable for dogs who are taking medicines with blood-thinning properties (for example aspirin), antibiotics or cancer drugs. It may also not be the best choice for those with stomach problems or peptic ulcers.

Instructions For Safe Use

Make sure you’re familiar with each active ingredient in your chosen supplement. Different ingredients may have different contraindications and drug interactions associated with their use. Prior to beginning treatment we recommend consulting with a vet and discussing the following:

  • Medication your dog is currently taking and any medical conditions they suffer from
  • Whether your chosen formulation is safe to use (mention additional ingredients)

Your vet will usually be able to advise you on which supplement to use if you’re unable to find one.

What Are The Benefits?

We will continue to learn about the benefits of the supplement as further studies are conducted. Currently is is believed that it may help with:

  • Allergies
  • Inflammation
  • Chronic fatigue
  • Interstitial cystitis
  • The prevention of cancer, heart attack and stroke

Current research suggests that it can slow the growth of cancer cells, and may be useful in cancer prevention. More about this here.

Side Effects

Adverse effects resulting from this supplement alone are uncommon, but may include:

  • Gastric effects
  • Headaches
  • Kidney damage

Kidney damage is very rare and is usually only a risk if your dog has pre-existing renal problems, or if massive overdose amounts are ingested. When bromelain is added, look for the following additional complications:

  • Increased heart rate
  • Mucous membrane irritation
  • Stomach problems

If you notice these adverse effects please get in touch with your vet right away to discuss how to proceed with treatment (if at all).