By Rania Gollakner, BS, DVM, MPH

What is eyebright?

Eyebright, from the Euphrasia officinalis plant, is an herbal supplement that is used as an antimicrobial (antiseptic), anti-inflammatory, and astringent, most commonly in dogs, cats, and horses. Eyebright contains substances such as tannins, aucubin, and quercetin that are the likely active ingredients.

It is typically used to supplement treatment for eye conditions such as conjunctivitis (inflammation of the tissues around the eyeball), allergies, or corneal ulcers. One common application is to treat conjunctivitis in cats caused by upper respiratory viruses.

"One common application is to treat conjunctivitis in cats caused by upper respiratory viruses."

Dietary supplements are substances that can be used to supplement the diet, such as vitamins, minerals, amino acids, herbs, botanicals, enzymes, and probiotics. While many supplements are sold over the counter, they still contain ingredients that have biological effects that should be managed by your veterinarian. Follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

There are differences in how countries regulate supplements. In the United States, these substances are not as vigorously regulated by the FDA as other medications, which means they can be sold without the manufacturer proving their effectiveness, safety, and without a guarantee of consistent or accurately reported ingredients. In Canada, products that have been evaluated for quality, safety, and effectiveness by Health Canada and authorized for sale will have a license number on the label.

How effective is eyebright?

Limited studies in animals and humans have been performed, but there is anecdotal evidence that eyebright works to treat skin and eye problems via anti-inflammatory, anti-microbial, and antioxidant actions.

How is eyebright given?

Eyebright is given by mouth in the form of a powder, capsule, or liquid tincture. It can also be formulated into a topical eye drop. Measure liquid forms carefully. It may be given with or without food, but if stomach upset occurs when given on an empty stomach, give future doses with food. This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the supplement?

If you miss a dose, give it when you remember, but if it is close to the time for the next dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Studies are limited for this supplement and therefore information regarding side effects is also limited. Rarely, irritation and inflammation may occur if your pet has an allergic or sensitivity reaction to the supplement.

Are there any risk factors for this supplement?

Studies are limited for this supplement and therefore information regarding risk factors is also limited. Eyebright should not be used in pets that are allergic to it.

Eyedrop formulations can become contaminated by bacteria, so do not use this supplement if it has been stored incorrectly, if the bottle tip has touched the skin or the eye, or if the supplement is past the expiration date.

Eyebright should be used cautiously in pregnant or nursing pets, or in pets that have had eye surgery or have diabetes. Some formulations of eyebright can be toxic if applied directly in the eye, so always check with your veterinarian before using this supplement in the eye.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease if taken orally.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with eyebright: insulin.

Vitamins, herbal therapies, and supplements have the potential to interact with each other, as well as with prescription and over the counter medications. It is important to tell your veterinarian about any medications (including all vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this supplement?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for side effects.

How do I store eyebright?

There are many formulations and preparations of eyebright; please follow the specific instructions on the label. In general, the capsules and the powders should be stored in a cool, dry place and protected from light.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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