The honest answer is that nothing works as well as proper contact lens solution, and most household substitutes carry real infection risk. If you are stuck overnight without solution, the least harmful option for soft lenses is sterile, preservative-free saline (the kind sold for wound irrigation or nasal rinsing) used purely as a short-term soak, not as a disinfectant. But even that falls short of what your lenses need, and everything else people reach for in a pinch, from tap water to saliva to bottled water, ranges from mildly risky to genuinely dangerous.
Why Contact Lens Solution Exists in the First Place
Contact lens solution is not just wet stuff in a bottle. A multipurpose solution does three jobs at once: it cleans debris off the lens surface, disinfects by killing bacteria and other microorganisms, and conditions the lens so it stays comfortable and holds its shape. Hydrogen peroxide-based systems take a different approach, using a stronger chemical reaction to sterilize and then neutralizing before the lens touches your eye. No household liquid replicates this combination. When you swap in a substitute, you are skipping the disinfection step entirely, and that is where the danger lives.
Tap Water Is the Most Common Mistake
Tap water feels harmless because you drink it, cook with it, and wash your face with it every day. But tap water is not sterile. Municipal treatment kills most disease-causing organisms, yet it does not eliminate everything, and the organisms that survive happen to be the ones most dangerous to contact lens wearers. Acanthamoeba, a single-celled parasite that thrives in plumbing biofilms, and Pseudomonas aeruginosa, an opportunistic bacterium, both colonize household water systems and can latch onto a contact lens or lens case when they come into contact with tap water.
A case-control study spanning over a decade found that cleaning or rinsing contact lenses with tap water roughly tripled the odds of developing Acanthamoeba or Fusarium keratitis, a painful corneal infection that can lead to permanent vision loss.1PubMed. Risk factors for acquisition and severity of Acanthamoeba and Fusarium keratitis in contact lens users-A case-control and clinical-epidemiological study, 2009-2020 That same study flagged other water-related risks too, including recreational surface water contact, which carried an even higher risk. Researchers have confirmed through genetic analysis that the specific Pseudomonas strains causing contact lens keratitis often trace directly back to contaminated lens storage cases, meaning the case itself becomes a breeding ground once tap water enters the picture.2PubMed. Molecular genetic investigations of contaminated contact lens storage cases as reservoirs of Pseudomonas aeruginosa keratitis
Beyond the microbial issue, tap water is hypotonic compared to your tears. Soft contact lenses absorb water and swell when placed in tap water, changing their shape and fit. When you put a water-swollen lens back on your eye, it can grip the cornea uncomfortably, distort your vision, and trap microorganisms against the eye’s surface. The organisms that thrive in plumbing biofilms, including Acanthamoeba and Pseudomonas, adhere readily to lenses and cases that have contacted contaminated tap water.3PubMed Central. Water Exposure is a Common Risk Behavior Among Soft and Gas-Permeable Contact Lens Wearers
Distilled Water, Bottled Water, and Filtered Water
People often assume that distilled water sidesteps the contamination issue since the distillation process removes microorganisms. Fresh, sealed distilled water is indeed initially sterile. But a study testing partially used bottles of distilled water from actual contact lens patients found that about one in eight samples had become contaminated.4PubMed Central. The dangers of distilled water in contact lens maintenance The moment you open the bottle and pour from it, you introduce organisms from the cap, your hands, and the surrounding air. The researchers recommended against using distilled water for contact lens care altogether.
Bottled drinking water is even less suitable. It is not distilled, and mineral content varies by brand. Some bottled water contains low levels of bacteria that are perfectly safe to swallow but not safe to park against your cornea for hours. Filtered water from a home pitcher or fridge dispenser is just treated tap water with some minerals and chlorine removed. The filters do not catch Acanthamoeba cysts or Pseudomonas. None of these options disinfect your lenses, and all of them introduce the same swelling problem as tap water.
Why Saliva Is a Terrible Idea
Popping a dry lens in your mouth is one of the oldest and worst contact lens habits. Your mouth hosts hundreds of bacterial species, many of which are harmless in the mouth but can cause serious eye infections. The warm, moist environment of the oral cavity is home to organisms like Staphylococcus aureus, Streptococcus species, and various fungi. These organisms stick to the lens surface and are then delivered directly to the cornea.
Eye care professionals have flagged saliva use as one of the riskiest behaviors among lens wearers. The bacterial load in a single drop of saliva dwarfs what you would find in a drop of tap water, and unlike water, saliva also contains enzymes and proteins that can coat the lens and feed microbial growth. If your lens falls on the floor and your instinct is to lick it clean, resist. You are better off throwing the lens away.
Homemade Saline and Store-Bought Saline
Some websites suggest mixing salt and water to make a DIY saline solution. This is genuinely dangerous. A literature review of microbial contamination across different lens care products found that homemade saline was contaminated in every single sample tested. Commercially bottled non-preserved saline fared only slightly better, with contamination rates between roughly a quarter and four-fifths of samples depending on the study. Even aerosol saline, which has no direct hand contact, showed contamination in up to about four in ten samples.5PubMed Central. Microbial Contamination of Contact Lenses, Lens Care Solutions, and Their Accessories: A Literature Review
The core problem is that saline, whether homemade or commercial, contains no antimicrobial agent. It is just salt and water. It keeps a lens hydrated and roughly matches the salt concentration of your tears, so it will not cause the same swelling that plain water does. But it does not kill anything. If you store a lens in saline overnight, bacteria present on the lens from a day of wear continue to multiply unchecked. Homemade saline compounds this problem because kitchen-mixed solutions are never sterile to begin with, the salt concentration is imprecise, and there is no buffer to keep the pH stable.
That said, if you truly have no contact lens solution and need to get through a single night, a sealed, sterile, preservative-free saline product (like a single-use saline ampoule sold at pharmacies for wound care or nasal irrigation) is the least bad substitute. Use it only once, put the lens in your eye the next morning, and get proper solution as soon as possible. Do not make this a habit.
What About Eye Drops?
Rewetting drops designed for contact lenses are safe to put in your eye while wearing lenses, but they are formulated for a quick refresh, not overnight storage. They contain lubricants and sometimes mild preservatives, but not a disinfecting agent. Soaking your lens in rewetting drops overnight is better than using tap water, since at least the solution is sterile when first opened and compatible with the lens material. But it is not disinfecting the lens, and any bacteria already on the lens surface will still be there in the morning.
Regular eye drops (like those for redness relief or allergy symptoms) are a worse choice. Some contain vasoconstrictors or antihistamines that can interact with lens materials, cause deposits, or irritate the eye when concentrated against the cornea under a lens. If the bottle does not say “for use with contact lenses,” do not use it as a lens soak.
The Cleanest Emergency Move
If you are traveling, staying at a friend’s house, or otherwise caught without solution, here is a practical priority list ranked from least risky to most risky:
- Throw the lenses away: If you wear daily disposables, this is the simplest answer. Put on your backup glasses and start fresh with a new pair tomorrow. Dailies are not designed for reuse under any circumstances.
- Buy solution: Most convenience stores and pharmacies carry travel-size bottles of multipurpose lens solution. A small bottle costs a few dollars and solves the problem entirely.
- Use sterile saline: A sealed, single-use preservative-free saline ampoule from a pharmacy is acceptable for a single overnight soak. It will not disinfect, but it will keep the lens hydrated without introducing contaminants. Clean and disinfect the lens properly the next morning.
- Use contact-lens-compatible rewetting drops: In a true pinch, filling a clean container with contact-lens-approved rewetting drops can keep a lens moist overnight. Again, no disinfection is happening.
Everything else, including tap water, bottled water, distilled water, saliva, and homemade salt water, falls into the “risk an infection” category. The severity of contact lens infections ranges from annoying (redness, irritation that clears in days) to devastating (Acanthamoeba keratitis can require months of painful treatment and sometimes corneal transplant). The stakes make it worth planning ahead.
Your Lens Case Matters Too
Even if you always use proper solution, the case you store lenses in can become a contamination source on its own. Research has shown that bacterial biofilms, sticky colonies of organisms that resist rinsing, form readily on the surfaces of contact lens cases.6PubMed. The effectiveness of various cleaning regimens and current guidelines in contact lens case biofilm removal Once established, these biofilms are difficult to remove even with rubbing and rinsing. Studies have found bacterial growth in about a third of lens cases and a quarter of solutions sampled from everyday wearers.7Elsevier / ScienceDirect (International Contact Lens Clinic). Clinical article Lens hygiene and care system contamination of asymptomatic rigid gas permeable lens wearers
Practical case hygiene makes a real difference. After inserting your lenses each morning, empty the case, rub the wells with clean fingers and fresh solution (not water), rinse with solution, and leave it open to air-dry face down on a clean tissue. Replace the case at least every three months, or whenever you open a new bottle of solution. If you are improvising storage in an emergency, at least use a container that has been freshly cleaned, like a small glass rinsed with boiling water and allowed to cool. A dirty shot glass or an old contact lens case with crusty residue is worse than the fluid you put in it.
How Long Can Lenses Survive Without Any Liquid?
Soft contact lenses are mostly water. A typical soft lens is somewhere between 38% and 75% water by weight, depending on the material. When removed from liquid and left in open air, the lens begins losing moisture within minutes. After a few hours, it shrinks, curls, and becomes rigid and brittle. At that point, putting it directly on your eye would be painful and could scratch the cornea.
A dried-out lens is not necessarily destroyed, though. If you rehydrate it in proper multipurpose solution for several hours (some manufacturers suggest at least four hours, though overnight is safer), it may return close to its original shape. Whether it is safe to wear depends on how long it was dry, what it was exposed to during that time, and whether it cracked or tore. Inspect it carefully for any damage before putting it back in your eye. If the edges look uneven, if it does not center on your eye, or if it feels uncomfortable after a few minutes of wear, discard it. A dried and rehydrated lens is more prone to harboring surface deposits and microorganisms in any micro-cracks that formed during dehydration.
For daily disposable lenses that have dried out, the answer is simpler: throw them away. They are thin, fragile, and not meant to survive a dehydration cycle. The cost of a single replacement lens is not worth the infection risk.
Sleeping in Your Lenses Instead
Some people reason that if they have no solution, they might as well just sleep in their contacts rather than risk a bad substitute. This is also not great. The same study that linked tap water exposure to keratitis found that napping in contact lenses nearly doubled the odds of developing a serious infection.1PubMed. Risk factors for acquisition and severity of Acanthamoeba and Fusarium keratitis in contact lens users-A case-control and clinical-epidemiological study, 2009-2020 During sleep, your eyelids are closed and oxygen delivery to the cornea drops sharply. A contact lens on top of a closed lid creates a warm, low-oxygen pocket that bacteria love. Extended-wear lenses approved for overnight use are made from high-oxygen-permeability materials specifically to reduce this risk, but standard daily-wear lenses are not.
That said, if your only two options are sleeping in your lenses for one night versus soaking them in tap water, sleeping in them is probably the lesser evil. One night of reduced oxygen is a short-term stress that a healthy cornea usually recovers from. Introducing Acanthamoeba from tap water is a potential long-term catastrophe. Remove the lenses first thing in the morning, give your eyes a break, and use proper solution from that point forward.
When to Worry After Using a Bad Substitute
If you did use tap water, saliva, or some other questionable liquid on your contacts, watch for symptoms over the following days. Redness, pain, light sensitivity, blurred vision, excessive tearing, or a feeling that something is stuck in your eye are all reasons to see an eye care professional quickly. Microbial keratitis typically takes one to several days to develop symptoms after exposure. Acanthamoeba keratitis is particularly insidious because it can initially mimic a minor irritation before progressing to severe pain that is out of proportion to the visible redness.
Early treatment makes an enormous difference. Bacterial keratitis caught early usually responds well to antibiotic drops. Acanthamoeba keratitis, if diagnosed late, can require months of intensive treatment and carries a real risk of permanent scarring. The single best thing you can do after an improvised lens soak is to be vigilant about your eyes over the next week and not dismiss symptoms as normal dryness or irritation.
Packing a Travel Kit
Most contact lens emergencies are preventable with a few dollars of preparation. A travel-size bottle of multipurpose solution, a spare lens case, and a pair of backup glasses fit in a bag pocket and eliminate the entire problem. If you wear dailies, tossing a few extra blister packs in your travel bag means you can always throw out a lens and start fresh. Some people keep a small kit in their car glove box or desk drawer for unexpected overnights. The solution does have a shelf life, typically printed on the bottle, but an unopened travel bottle lasts a year or more. Interestingly, research suggests that the printed expiration date does not reliably predict whether a solution has maintained its sterility; contamination depends more on how the bottle has been handled and stored than on calendar age alone.7Elsevier / ScienceDirect (International Contact Lens Clinic). Clinical article Lens hygiene and care system contamination of asymptomatic rigid gas permeable lens wearers Still, using a bottle well within its printed date and keeping it sealed until needed is the safest bet.