Using a Boric Acid Eye Wash

Benefits, uses, and side effects of treatment

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Boric acid eyewashes have been used for generations to cleanse irritated eyes and fight infection. Boric acid, also known as hydrogen borate (H3BO3), is a weak acid derived from the mineral boron that is widely used in over-the-counter (OTC) antiseptics and astringents. In its natural form, boric acid is a colorless or white crystal that can be finely ground into a powder and dissolved in water.

While toxic if ingested, boric acid has beneficial properties when used as an eyewash. Most of these washes are prepared in an isotonic saline solution comprised of purified water, sodium chloride (salt), and other ingredients.

A boric acid eyewash can be effective for irrigating eyes exposed to grit or other foreign objects. It can also be used to ease dry, irritated, or burning eyes.

Potential side effects of boric eye wash
Verywell / Brianna Gilmartin


Because the level of boric acid in an OTC eyewash is extremely low—generally around 0.02 percent—it poses no harm to the eyes or surrounding tissues. According to the European Medicines Agency, each 50 microliter (mL) drop contains only around 0.004 milligrams (mg) of boron, well below the allowable limit of 1.0 mg per day.

When used in an eyewash, boric acid has a number of useful properties:

  • Mild antiseptic properties: It can inhibit bacterial and fungal growth and may help prevent certain mild infections.
  • Compatible with your eye tonicity: What this means is that the drops neither diffuse nor dilute the essential chemicals in your eye fluid. This makes it ideal for irrigation as it won’t undermine the eye’s natural chemistry.
  • Acts as a buffering agent: Buffering agents are able to maintain the pH balance of a solution even if an alkaline or acid is added. By doing so, other active or inactive ingredients may be added without altering the pH balance of the solution.


There are a wide variety of boric acid eyewashes on drugstore shelves. Most are used to cleanse and refresh the eyes when mildly irritated. Others can be used to support the treatment of an eye infection or other conditions affecting the eye. These include antihistamine eye drops like Visine-A or Opcon-A, both of which contain boric acid.

Boric acid eye washes may be used to rinse foreign substances from the eye, including chlorinated water, dust, smoke, chemicals, and smog. It can also be used to relieve eye irritation caused by:

The drops, while effective, don’t necessarily treat the underlying condition but are rather used to ease eye discomfort. This is especially true with fungal eye infections or severe allergy symptoms, both of which require multiple treatment approaches.

While boric acid is known to exert antibacterial and antifungal properties, the actual effect is minimal at such low concentrations. As such, if you suspect you have an eye infection, it is best to have it seen by a healthcare provider rather than treating it with an OTC eye solution.

How to Use an Eye Wash

Depending on your need and the brand of solution used, a boric acid eyewash may be applied with an eye dropper or eyecup. 

Always read the product label and follow the instructions as written. If in doubt, speak with your healthcare provider or pharmacist to ensure the correct usage.

If you wear contact lenses, be sure to remove them before using a boric acid eye wash. The preservatives used in some solutions can be absorbed by the lenses and cause discoloration. Wait for at least 15 minutes following an eyewash before replacing your contacts.

You should avoid using the eyewash if you have sores or open wounds in or around the eyes. Most importantly, never use an eyewash that is either cloudy or past its expiration date.

To Use an Eyedropper

  1. Open the eye dropper bottle.
  2. Tilt your head back and tug the lower eyelid gently downward.
  3. Position the dropper over your eyeball without touching it.
  4. Apply only the number of drops recommended.
  5. Close your eyelid to draw the liquid over the eyeball surface.
  6. Blot any excess fluid from around your eye.
  7. Repeat with the other eye, if needed.
  8. Rinse the cap with water and replace it tightly.

To Use an Eye Cup

  1. Open the bottle.
  2. Pour as much eyewash into the cup as is recommended.
  3. Tilt your head forward over the kitchen sink.
  4. Place the cup firmly around the eye.
  5. Tilt your head back and open the eye.
  6. Move your eyeball around so that it is fully immersed in fluid.
  7. Tilt your head forward.
  8. Pour the contents of the cup down the drain.
  9. Repeat with the other eye, if needed.
  10. Rinse the cap with water and replace it tightly.

While it is best to use a disposable eyecup, you can reuse a cup if you wash it thoroughly with hot water and soap and avoid touching the rim or inside of the cup with your fingers.

Side Effects

Boric acid eye drops are considered safe if used as directed. Some people may experience a slight tingling sensation or momentary blurriness after the wash. Side effects like these tend to be mild and usually resolve within a few seconds or minutes.

However, you should stop using the eyewash and call your healthcare provider if the sensations persist or you experience any of the following:

  • Eye redness
  • Eye pain
  • Severe stinging or burning
  • Eyelid inflammation
  • Itchy eyes
  • Persistent weepy eyes
  • Vision changes
  • Worsening of your eye condition

While allergic reactions to a boric acid eye wash are rare, they do occur and may manifest with symptoms of contact dermatitis (redness, rash, inflammation).


Never use a boric acid eye wash together with a contact lens wetting solution or any other ophthalmologic solution containing polyvinyl alcohol (PVA). Doing so decreases the pH balance of the eyewash, making it far more acidic and irritating to the eyes.

A Word From Verywell

Boric acid eye washes have been a mainstay of eye care for many families for generations. While it is easy to find eyewash recipes online, making your own should be avoided as it is more likely to cause harm than good. The wrong proportion of boric acid to water can end up causing a serious eye injury. Moreover, there are simply too many opportunities for contamination to take the risk. In the end, it is better to shop around and find a reasonably priced OTC brand, some of which are as low $4 for a 4-ounce bottle.

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Article Sources
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  1. José AC, Castelo branco B, Ohkawara LE, Yu MC, Lima AL. [Use conditions of boric acid solution in the eye: handling and occurrence of contamination]. Arq Bras Oftalmol. 2007;70(2):201-7. DOI: 10.1590/s0004-27492007000200004

  2. Overview of comments received on the draft 'Questions and answers on boric acid’ (EMA/CHMP/619104/2013).

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