No liquid you have around the house is a safe substitute for contact lens solution. Not tap water, not bottled water, not distilled water, not saliva, not homemade salt water. Every one of these carries a real risk of contaminating your lenses with microorganisms that can cause painful, sometimes sight-threatening eye infections. The safest thing to do when you run out of solution is to throw your lenses away if they are disposable, or keep them dry in a clean case and buy proper solution before wearing them again. That said, there are some liquids that are less dangerous than others, and understanding why each common substitute fails can help you make a smarter decision in a genuine emergency.
Why Tap Water Is the Worst Option
Tap water is the substitute most people reach for first, and it is the most dangerous. Municipal water supplies contain low levels of bacteria, fungi, and amoebae that are harmless when swallowed but dangerous when pressed against your cornea by a contact lens. The organism eye doctors worry about most is Acanthamoeba, a free-living amoeba found in virtually all water sources, including treated tap water, well water, and even some bottled water. Acanthamoeba keratitis, the infection it causes, is strongly linked to contact lens wear and can lead to months of painful treatment, corneal scarring, and in severe cases, loss of vision.
The connection between contact lenses and Acanthamoeba infection is well established. Contact lens wear may account for up to 95% of reported Acanthamoeba keratitis cases, with water exposure being a key risk factor.1Europe PMC. How Could Contact Lens Wearers Be at Risk of Acanthamoeba Infection? A Review Water exposure during lens wear is associated with complications ranging from sterile corneal inflammation to sight-threatening infections.2Cornea. Water Exposure and the Risk of Contact Lens–Related Disease This is not a theoretical risk. In a study of patients hospitalized with contact lens-related infectious keratitis, about a third had been rinsing their lenses with tap water, and water exposure while wearing contacts was significantly more common among patients who developed fungal keratitis.3PubMed. Contact lens-associated infectious keratitis: microbiological profile, management, and hygiene behaviors in a tertiary eye hospital
Beyond contamination, tap water causes a physical problem with soft lenses. Soft contacts are designed to maintain a specific shape and water content using solutions that match the salt concentration of your tears. Tap water is hypotonic, meaning it has far less salt than your tears. Soft lenses absorb tap water and swell, changing shape, becoming tighter on your eye, and trapping any waterborne organisms between the lens and your cornea. That tight fit makes it harder for your natural tear film to flush debris away.
Distilled Water, Bottled Water, and Other “Clean” Waters
People assume that distilled or bottled water must be sterile, but neither is. Research going back decades has found that commercially available distilled water, including brands specifically marketed for use with soft contact lenses, can be contaminated with gram-negative bacteria right out of the bottle.4American Journal of Ophthalmology. Pseudomonas Corneal Ulcers Associated with Soft Contact-Lens Wear A separate study that tested partially used bottles of distilled water found that about one in eight samples was contaminated.5PubMed. The dangers of distilled water in contact lens maintenance Once you open a bottle and pour from it, airborne organisms and organisms on your hands can colonize the remaining water quickly.
Bottled spring water and mineral water are even worse. They are not treated to the same standard as distilled water and often contain higher microbial loads. And like tap water, all of these are hypotonic, so they cause the same swelling and shape-change problem with soft lenses. The bottom line is that “clean-looking” water is not sterile water, and even truly sterile water lacks the preservatives and disinfecting agents that contact lens solution provides.
What About Saline Solution?
Saline is the substitute that sounds most reasonable, and it is the least harmful of the bad options, but it still falls short. Pharmacy saline solution (the kind sold for wound irrigation or nasal rinsing) is sterile when sealed and has the right salt concentration to avoid swelling your lenses. The problem is that saline does not disinfect. It will not kill bacteria, fungi, or amoebae. If your lenses were contaminated before you stored them, saline will keep those organisms alive and comfortable. If the saline bottle has been opened and used before, the saline itself may no longer be sterile.
Homemade saline, sometimes suggested online as a “recipe” using table salt and water, is genuinely dangerous. You cannot reliably achieve the right salt concentration at home, and kitchen salt often contains anti-caking agents and iodine that irritate the eye. The water you mix it with carries all the risks described above. Do not make your own saline for contact lenses under any circumstances.
If you must use pharmacy saline in an absolute pinch, treat it as a very temporary measure. Store the lenses in it for the shortest time possible, and thoroughly clean them with proper multi-purpose solution before putting them back in your eyes. Ideally, discard the lenses entirely if they are daily disposables or near the end of their replacement cycle.
Artificial Tears and Rewetting Drops
Preservative-free artificial tears are designed to be compatible with the eye and are sometimes used directly with contact lenses in place to relieve dryness. Research shows that both preserved and preservative-free artificial tears and rewetting drops are generally safe when used with contact lenses and have minimal impact on the eye’s surface, especially the preservative-free versions.6PubMed. A Review of the Compatibility of Topical Artificial Tears and Rewetting Drops with Contact Lenses However, “safe to put in your eye while wearing lenses” is very different from “safe to soak your lenses in overnight.”
Artificial tears are not formulated to disinfect. They do not contain the antimicrobial agents found in multi-purpose solutions. Soaking a lens overnight in a small pool of artificial tears gives any surface bacteria hours to multiply without opposition. Additionally, preserved artificial tears contain chemicals like benzalkonium chloride that can absorb into soft lens material over hours of soaking, potentially irritating your eyes when you reinsert the lenses. If you only have preservative-free single-use vials available, they are probably the least risky emergency option after pharmacy saline, but you should still clean your lenses with real solution before wearing them again.
What Actually Grows on Your Lenses
Understanding what lives on improperly stored lenses helps explain why eye care professionals are so emphatic about this topic. Bacteria do not just float around on a lens surface. They form biofilms: organized colonies embedded in a sticky matrix that anchors them to the lens material and shields them from your immune system and even from disinfecting solutions. Pseudomonas aeruginosa, Staphylococcus aureus, and Serratia marcescens all form dense biofilms on silicone hydrogel contact lenses, building up in multiple layers with visible protective matrix material.7PubMed Central. Increased resistance of contact lens-related bacterial biofilms to antimicrobial activity of soft contact lens care solutions
Biofilm formation varies by lens material. Some hydrogel materials attract more bacterial attachment than others, with Staphylococcus aureus and Pseudomonas aeruginosa being the heaviest biofilm producers on common hydrogel-based lens materials.8PubMed Central. Influence of Contact Lens Materials and Cleaning Procedures on Bacterial Adhesion and Biofilm Formation Once a biofilm is established, it is much harder to remove. Fresh disinfecting solution poured over an established biofilm does not necessarily kill everything underneath. This is why proper daily cleaning with a rub-and-rinse step matters so much, and why soaking in a non-disinfecting liquid is so risky: you are giving organisms time to set up a colony that your solution may struggle to clear later.
Acanthamoeba is especially problematic. When this amoeba encounters a contact lens surface, it can form protective cysts and aggregate into clusters that resist disinfection far more effectively than individual organisms would.9PubMed Central. Acanthamoeba spp. aggregate and encyst on contact lens material increasing resistance to disinfection Some lens materials promote this aggregation more than others, but the general principle is the same: once Acanthamoeba establishes itself, even proper multi-purpose solutions may not fully clear it.
Your Actual Options in an Emergency
When you are stuck without solution, your choices depend on what kind of lenses you wear and what you have access to.
- Daily disposables: Throw them away. This is the simplest and safest option. Dailies are designed for a single use and cost relatively little per pair. Wearing them again after soaking in any non-approved liquid is not worth the risk.
- Extended-wear lenses: If your lenses are approved for overnight wear and are already in your eyes, sleeping in them for one night is generally less risky than taking them out and soaking them in water. This is not ideal, but the FDA has cleared certain silicone hydrogel lenses for continuous wear specifically because they allow enough oxygen through to the cornea during sleep.
- Two-week or monthly lenses: If you must remove them and have no solution at all, place them in a clean, dry container. Let them dry out rather than soaking them in tap water. A dried-out lens is damaged and uncomfortable, but you can try rehydrating it in proper solution later. Whether the lens will be wearable after that depends on how long it was dry and the lens material. Many will be too warped to use, but a warped lens is better than an infected cornea.
- Buy solution: Many gas stations, hotel front desks, airports, and 24-hour pharmacies carry travel-sized bottles of multi-purpose solution. Before you reach for the bathroom faucet, check whether any of these are accessible. A $5 travel bottle is always cheaper than treating an eye infection.
How Common Risky Behavior Actually Is
If you have ever stored or rinsed your lenses in tap water, you are far from alone. Surveys of contact lens wearers reveal that water exposure is remarkably common. Among soft contact lens wearers, about 86% reported showering while wearing their lenses, and 62% reported swimming in them.10PubMed Central. Water Exposure is a Common Risk Behavior Among Soft and Gas-Permeable Contact Lens Wearers About 10% of soft lens wearers reported always or fairly often rinsing their lenses with tap water, despite no soft lens care system recommending this. Perhaps most concerning, wearers who did rinse or store lenses in water consistently rated their infection risk as low, suggesting that the dangers of water exposure are not getting through to most people.
Gas-permeable (rigid) lens wearers are even more likely to use tap water: about a third reported storing their lenses in it, and 91% reported rinsing lenses with tap water at least occasionally. The rigid materials are less porous than soft lenses, which may partially explain why some practitioners historically were more relaxed about water contact with GP lenses, but the infection risk is still real.
Why Your Lens Case Matters More Than You Think
Even if you always use proper solution, a dirty lens case can undermine your efforts. Research consistently finds that well over half of all lens cases are contaminated with bacteria, with many studies documenting contamination rates as high as 81%.11PubMed Central. Microbial Contamination of Contact Lenses, Lens Care Solutions, and Their Accessories: A Literature Review The contamination rate in lens cases is actually higher than on the lenses themselves. Unlike lens surfaces, which tend to harbor mainly bacteria, lens cases often contain mixed populations of bacteria, fungi, and protozoa, making them a more dangerous reservoir overall.
A contaminated case can act as a persistent source of organisms that transfer to your lenses every time you store them.12PubMed. Contact lens hygiene compliance and lens case contamination: A review Simply adding fresh solution to a contaminated case does not reliably kill biofilms that have adhered to the case walls. Even following manufacturer cleaning guidelines does not always eliminate case contamination: one study found case contamination rates of 82% in the group following standard manufacturer instructions and 72% in a group following an alternative regimen.13PubMed. Impact of lens case hygiene guidelines on contact lens case contamination
The practical takeaway: replace your lens case at least every one to three months. Between replacements, rinse it with fresh solution (never water), wipe it with a clean tissue, and leave it open to air-dry face down. If you are in a situation where you run out of solution and use a substitute liquid in a case that has not been replaced recently, you are compounding two separate contamination risks.
How Hydrogen Peroxide Systems Work Differently
If you have a bottle of hydrogen peroxide-based lens cleaner in your bathroom cabinet instead of multi-purpose solution, it is worth understanding what you have and why it is not interchangeable with multi-purpose solution in an emergency. Hydrogen peroxide systems use 3% hydrogen peroxide to disinfect lenses, then neutralize the peroxide before you put the lenses back in your eyes. This neutralization step is critical. Un-neutralized hydrogen peroxide on a contact lens will cause severe stinging and can damage your corneal surface.14PubMed Central. Comparison of hydrogen peroxide contact lens disinfection systems and solutions against Acanthamoeba polyphaga
In one-step systems, a platinum disc in the special case catalyzes the breakdown of peroxide into water and oxygen over several hours. In two-step systems, you add a neutralizing tablet or solution after the disinfection soak is complete. Either way, you need the correct case and the correct timing. You cannot pour hydrogen peroxide lens solution into a regular flat lens case and call it good. You also cannot cut the neutralization time short because you are in a hurry. If you have a hydrogen peroxide system at home but you are traveling without the special case, the peroxide solution alone is not usable.
Hydrogen peroxide systems do tend to produce cleaner lens cases. Research comparing disinfection methods found that hydrogen peroxide users had significantly lower case contamination rates than users of other chemical disinfection systems. This is partly because peroxide is a stronger broad-spectrum antimicrobial than the preservatives in most multi-purpose solutions, and partly because the special cases are designed to be replaced with each new bottle.
Microbial Keratitis and the Real Stakes
The worst-case outcome of poor lens hygiene is microbial keratitis, an infection of the cornea that can permanently damage vision. Estimates suggest that for every 10,000 contact lens wearers per year, there are roughly 2 to 5 cases of microbial keratitis.15PubMed Central. A Review of Contact Lens-Related Risk Factors and Complications Those numbers sound small, but the consequences are disproportionately severe. Treatment often involves weeks or months of hourly antibiotic or antifungal eye drops, and in cases involving Acanthamoeba, treatment can stretch past a year. Some patients require corneal transplants.
The risk factors that consistently show up in studies of contact lens-related keratitis are exactly the behaviors being discussed here: sleeping in lenses, using water to rinse or store lenses, extending lens wear beyond the recommended replacement schedule, and poor case hygiene. Each risk factor alone raises your odds modestly, but they tend to cluster. Someone who runs out of solution and soaks their lenses in tap water is also more likely to overwear lenses and skip case cleaning. The risks compound.
None of this is meant to terrify you into never wearing contacts. The vast majority of lens wearers never develop a serious infection. But the infections that do happen are disproportionately concentrated among people who cut corners with hygiene, and soaking lenses in a non-approved liquid is one of the most common corners to cut. A single night of tap water storage probably will not blind you, but it is the kind of habit that, repeated over months, substantially increases the odds of a bad outcome.
Packing a Backup
The easiest way to avoid this dilemma entirely is to keep a small backup supply wherever you might need it. A travel-sized bottle of multi-purpose solution and a spare lens case weigh almost nothing. Toss one in your overnight bag, your gym bag, your desk drawer at work, and your car’s glove box. If you wear daily disposables, keeping a spare pair in your wallet or purse eliminates the problem altogether, since you can just throw the current pair away and start fresh. For monthly or two-week lens wearers, carrying a single-dose vial of preservative-free saline as an absolute last resort is better than nothing, though it still does not disinfect. The point is to make it so you never actually face the question of what else you can soak your lenses in, because the answer is genuinely nothing that works well.