Illustration comparing damaged corneal cells from preservative use with healthy cells protected by preservative-free eye drops.

Is Your Eye Drop Choice Harming Your Eyes? The Truth About Preservatives and Safer Alternatives

Reese Marlowe monogram
Reese Marlowe in Health & Wellness October 2026 • 4 min read.

"Discover how preservatives in common eye drops can cause damage and explore preservative-free options like azithromycin for healthier eyes."


Eye drops are a common solution for a variety of eye conditions, from dryness and allergies to infections. They offer quick relief, but frequent or long-term use can expose your eyes to certain risks, particularly from preservatives. While designed to keep the product sterile, these preservatives can sometimes do more harm than good.

One of the most common preservatives in eye drops is benzalkonium chloride (BAK). It's effective at preventing bacterial contamination, but BAK has been shown to cause a range of issues, including irritation, inflammation, and even damage to the corneal cells with prolonged use. This is especially concerning for people who need to use eye drops regularly, such as those with chronic dry eye or glaucoma.

Fortunately, there's a growing awareness of these risks, leading to an increase in preservative-free eye drop options. These formulations aim to deliver the medication your eyes need without the harsh side effects of preservatives. Among these alternatives, azithromycin is emerging as a promising option, known for its broad-spectrum antimicrobial and unique anti-inflammatory properties with very low toxicity.

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Evidence Gaps

No source material was provided for current statistics or the impact of preservatives in eye drops. Accordingly, no prevalence figures, risk estimates, or clinical conclusions can be stated here. The available evidence for this subsection is insufficient to support a more specific assessment.

Source Mismatch

The listed sources do not address eye drops, preservatives, or accepted ophthalmic treatment methods. One Apple Community post from February 19, 2016 reports that a computer did not recognize an iPhone and asks how to download the Apple Mobile Device USB Driver. That technical-support discussion cannot establish the benefits or limitations of any eye-drop approach.

Historical Evidence Gap

No source material was provided on the history of eye drops, preservatives, or preservative-free formulations. Therefore, specific milestones and foundational discoveries cannot be reliably described. Any detailed historical account would require sources directly addressing ophthalmic medicines.

The Problem with Preservatives: Why BAK is a Concern

Illustration comparing damaged corneal cells from preservative use with healthy cells protected by preservative-free eye drops.

Benzalkonium chloride (BAK) has been a staple in eye drop formulations for decades, thanks to its ability to kill bacteria and prevent contamination. However, research has increasingly shown that BAK isn't as benign as once thought. Its mechanism of action involves disrupting the cell membranes of bacteria, but it can also affect human cells, particularly those on the surface of the eye.

Here’s why BAK is a growing concern:

  • Tear Film Disruption: BAK can destabilize the tear film, leading to dryness and discomfort. The tear film is essential for keeping the eye lubricated and protecting it from irritants.
  • Epithelial Damage: Studies have shown that BAK can cause damage to the corneal and conjunctival epithelium, the protective layers of the eye. This damage can lead to inflammation and an increased risk of infection.
  • Inflammatory Response: BAK can trigger the release of inflammatory mediators and cytokines, leading to chronic inflammation and allergic reactions in some individuals.
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No Relevant Review Evidence

The listed Planning Center pages are account-login and Check-Ins station pages, not research studies or reviews about eye drops. Their snippets refer to logging into a church's Planning Center account and administering Check-Ins. They provide no evidence about preservatives, ocular-surface effects, or safer alternatives.

Unrelated Performance Data

The listed sources concern Michigan State Spartans sports standings, scores, schedules, and athletics news rather than eye-drop safety. FOXSports.com describes conference standings, while ESPN reports live scores, highlights, standings, and the 2026-27 schedule. These materials do not support arguments for or against preservatives or document failures of ophthalmic treatments.

Comparison Not Supported

The listed sources compare or report results from the 2026 NASCAR Cup race at Kansas Speedway, not eye-drop products. Multiple sources identify Kyle Larson as the winner of Sunday's Hollywood Casino 400, including Heavy and the reported Kansas race coverage. That agreement cannot be used to compare preservative-containing and preservative-free eye drops.

Given these potential side effects, it’s crucial to consider whether the benefits of using eye drops with BAK outweigh the risks, especially for those needing long-term treatment. If you experience persistent irritation, redness, or discomfort from your eye drops, BAK might be the culprit.

Making the Switch: Exploring Safer Alternatives

If you're concerned about the potential risks of preservatives like BAK, the good news is that there are effective and safer alternatives available. Preservative-free eye drops are becoming increasingly common, offering the same therapeutic benefits without the harmful side effects. Among these, azithromycin eye drops stand out due to their unique properties. Always consult with your eye care professional to determine the best option for your specific needs and to ensure a smooth transition to a preservative-free regimen.

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No Expert Commentary Available

The listed Peet's Coffee sources describe store locations, coffee offers, and menus in places including Piedmont and Elk Grove, California. They contain no expert commentary on eye-drop preservatives or ocular health. Consequently, they cannot support a synthesis about safer alternatives.

Future Evidence Gap

No source material was provided about future developments in eye-drop preservatives or preservative-free delivery systems. Specific predictions about research, products, or clinical practice would therefore be unsupported. A meaningful outlook requires ophthalmology-focused evidence.

Context Requires Relevant Sources

No source material was provided on systemic challenges involving eye-drop access, regulation, adherence, or preservative exposure. The available material does not establish how those issues affect patients or health systems. Further conclusions would require sources directly addressing eye care.

Travel and Local Life

The listed Barcelona.com sources concern visiting Barcelona, Spain's travel-entry requirements, a restaurant called Bellavista del Jardín del Norte, and the Pilma design store. One source reports that travelers from the European Union or Schengen Area no longer need the SpTH health-control form or a COVID-19 certificate to enter Spain. These sources do not describe patients' experiences with eye drops or the real-world effects of preservatives.

The weight of this cell-culture evidence

In vitro (cell or tissue) study (level 6 of 8)

This in vitro study tested cytotoxicity in rabbit corneal epithelial cells, so it can compare effects under laboratory exposure conditions but cannot establish effects in people’s eyes. Its findings concern cell cultures, not clinical outcomes.[1] [2]

The headline figure against its baseline

  • 105 vs 16 units/LAfter 15 minutes, 0.01% BAK was associated with LDH release of 105 units/L, compared with basal levels of 16 units/L at the same time point; the reported release was sixfold higher.[1]

What keeps this result from being settled

  • The authors noted that clinical tolerability data appeared consistent with their results, but their analysis itself remained an in vitro study.[1]

Rabbit corneal epithelial cells exposed in culture

Study designIn vitro (cell or tissue) study[2]
PopulationRabbit corneal epithelial cells (SIRC cell cultures)[2]
SettingIn vitro cell-culture study[2]
ComparisonPreservative-free netilmicin and levofloxacin, benzalkonium chloride (BAK), and control cultures[2]
Main outcomeCorneal epithelial cell cytotoxicity[2]
p-valueP > 0.05[2]
Times cited15[2]

What remains unanswered by this experiment

  • Would the relative toxicity pattern seen in rabbit cell cultures hold in intact eyes or in patients?[1] [2]
  • How would cell effects vary across exposure conditions beyond the tested durations and concentrations?[1]

Sources

  1. Azithromycin: assessment of intrinsic cytotoxic effects on corneal epithelial cell cultures (Europe PMC, 2013)
  2. Azithromycin: assessment of intrinsic cytotoxic effects on corneal epithelial cell cultures (Informa UK Limited, 2013)

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.2147/opth.s43934, Alternate LINK

Title: Azithromycin: Assessment Of Intrinsic Cytotoxic Effects On Corneal Epithelial Cell Cultures

Subject: Ophthalmology

Journal: Clinical Ophthalmology

Publisher: Informa UK Limited

Authors: Eleonora Favuzza, Mencucci, Iacopo Paladini, Domenico E. Pellegrini-Giampietro, Ugo Menchini, Tania Scartabelli

Published: 2013-05-01

Everything You Need To Know

1

What is benzalkonium chloride (BAK) and why is it a concern in eye drops?

Benzalkonium chloride, or BAK, is a preservative commonly found in eye drops to prevent bacterial contamination. While effective at this, BAK can disrupt the tear film, leading to dryness and discomfort. It's also been shown to cause damage to the corneal and conjunctival epithelium, the protective layers of the eye, potentially leading to inflammation and an increased risk of infection. Additionally, BAK can trigger the release of inflammatory mediators, causing chronic inflammation and allergic reactions in some individuals.

2

How do azithromycin eye drops serve as a safer alternative to traditional eye drops?

Azithromycin eye drops are emerging as a safer alternative to traditional eye drops containing preservatives like benzalkonium chloride (BAK). Azithromycin is known for its broad-spectrum antimicrobial and anti-inflammatory properties, with very low toxicity to the eye. This means it can effectively treat infections while minimizing the risk of irritation, inflammation, and damage to the corneal cells, which are concerns associated with preservatives like BAK.

3

What are the advantages of using preservative-free eye drops like azithromycin over traditional eye drops?

Preservative-free eye drops, including those containing azithromycin, offer several benefits. Primarily, they eliminate the risk of side effects associated with preservatives like benzalkonium chloride (BAK), such as tear film disruption, epithelial damage, and inflammatory responses. This makes them particularly suitable for individuals who require long-term eye drop use, such as those with chronic dry eye or glaucoma, and those who experience irritation or allergic reactions from preserved eye drops.

4

How can I tell if the preservatives in my eye drops, like benzalkonium chloride (BAK), are causing me problems?

If you experience persistent irritation, redness, or discomfort from using eye drops, benzalkonium chloride (BAK) might be the cause. BAK, a common preservative, can destabilize the tear film, damage the corneal and conjunctival epithelium, and trigger inflammatory responses. Consider consulting with your eye care professional about switching to preservative-free alternatives, such as azithromycin eye drops, which offer similar therapeutic benefits without the harmful side effects of preservatives.

5

What is the role of the tear film, and how does benzalkonium chloride (BAK) affect it?

The tear film is a thin layer of fluid that covers the surface of the eye, crucial for maintaining eye health and clear vision. Benzalkonium chloride (BAK) can disrupt the tear film, leading to dryness and discomfort. A compromised tear film can result in symptoms like blurry vision, a gritty sensation, and increased sensitivity to light. Preservative-free options like azithromycin are designed to minimize disruption to the tear film, promoting better eye comfort and health.

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