What is BAK?

Benzalkonium chloride, a preservative commonly used in eyedrops.

Why should I care about BAK?

#1: It's in most prescription eye drops, and many over the counter eye drops.

#2: It's known to cause or exacerbate dry eye in multiple ways.

Benzalkonium chloride (BAK) is a common preservative that is believed to be damaging to the eyes in up to seven different ways, according to TFOS DEWS II's Iatrogenic Dry Eye Report (see section 4.2.3.1). Unfortunately, not only is this preservative used in most prescription eye drops - for the vast majority of which, no preservative-free version is available - but it is also used in many over-the-counter eyedrops without any warning on the label that mentions the preservative. Consumers sometimes use drops every day for years without any idea of the long term side effects, on the assumption that if it is sold over the counter, it must be safe. Consumers who are taking prescription eye drops on a daily basis for long periods are often similarly unaware of the ocular surface risks involved.

Read more about BAK here. 

How (not) to use this information

Don't: Please don't stop taking a drug your doctor prescribed just because it's on this list!

Don't: Assume that if it's not on this list then it's OK. These lists are not exhaustive. Check the label to be sure.

Do: Look up your eye drops to see if any of them have BAK.

Do: Bear in mind that while I have included active ingredients so that you can find equivalents and generics, equivalents and generics may be different from the original name brand - they may have a different preservative, or have a different concentration of the preservative.

Do: Have a conversation with your eye doctor to see if there is an alternative that is either preservative-free or contains a less harmful preservative.

A conversation may seem like a small thing. IT'S NOT SMALL. Our collective conversations are our most powerful tools to influence the eye care professions and the industries that cater to them and us, which can change the future of eye care and reduce the incidence of preventable dry eye caused by preservatives. 

So please, talk, ask questions, and keep the conversation about preservatives flowing.

Over-the-counter eye drops with BAK

This list contains popular lubricant drops, allergy drops, redness relievers and combination drops. Unfortunately, in some cases the manufacturers refused to provide BAK concentration details. If we're missing a product sold in the US, please contact us so we can add it.

BAK-free alternatives to consider:

• For dry eye: There are so many that there is absolutely no reason why anyone would ever knowingly choose a BAK-preserved dry eye drop. Please see our lubricant eye drop ingredient list. All preservative-free lubricants are marked.
• For allergy: Alaway PF (Bausch & Lomb) became available OTC in 2021.
• For redness relief: Clear Eyes Pure Relief Multi-Symptom. But please bear in mind that while it is preservative-free, it is a vasoconstrictor which is associated with a 'redness rebound' effect. Lumify is the only redness reliever on the US market believed not to be associated with redness rebound, however, it is preserved with 0.01% BAK.

Prescription eye drops with BAK

These lists contain commonly prescribed prescription eye drops  Our sources are the FDA and the manufacturer's websites. Please note that these lists are not exhaustive. Please contact us with any additions or corrections.

1. Glaucoma eye drops

Glaucoma eye drops without BAK:

• Travatan Z (travoprost 0.004%) is preserved with sofZia
• Alphagan P (brimonidine tartrate 0.1%) is preserved with Purite
• Zioptan (tafluprost 0.005%) is preservative-free
• Cosopt PF (dorzolamide hydrochloride and timolol maleate) is preservative-free
• Timoptic 0.25% and 0.5% in Ocudose (timolol maleate) is preservative-free

2. Allergy eye drops

Allergy eye drops without BAK

There are no preservative free prescription allergy drops on the US market to the best of our knowledge.

3. Steroid eye drops

Steroid eye drops without BAK

• Durezol (difluprednate) is preserved with sorbic acid

4. Antibiotics

5. NSAID eye drops

6. Other eye drops

Sources

Our sources are almost exclusively manufacturers and the FDA (see links). If we had to request BAK concentrations, notes of the outcome are below.

(1) Lumify: July 24, 2018 tweet from Bausch & Lomb's Twitter account replying to question from @dryeyezone. BAK concentration data is redacted from Lumify's FDA documentation. 

(2) We requested information on BAK concentrations in Visine brand eye drops. Here is their reply, dated 2/6/2019: 

Additional reading

• TFOS DEWS II Iatrogenic Dry Eye Report (A comprehensive review; Gomes et al, The Ocular Surface, 2017) - Contains extensive references prior to 2017
• The Eye Drop Preservative Benzalkonium Chloride Potently Induces Mitochondrial Dysfunction and Preferentially Affects LHON Mutant Cells (Datta et al, IOVS, April 2017)
• Glaucoma therapy: preservative-free for all? (J. Thygesen, Clinical Ophthalmology, April 2018)