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 in Health & Wellness November 2025 • 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.

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.

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.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.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

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.

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.

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.

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.

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.