Getting a speck of dust, an eyelash, or a chemical in the eye is a common experience that prompts the question of how to flush it out. Many people instinctively reach for bottled drinking water as a quick solution. However, bottled drinking water is generally not a safe or recommended solution for routine eye rinsing. This is especially true for contact lens wearers, as the composition of bottled water poses risks to the delicate surface of the eye.
Why Bottled Drinking Water is Not Recommended
The primary concern with using bottled drinking water for eye rinsing is its lack of guaranteed sterility, despite being safe for consumption. Unlike specialized eye products, bottled water is not required to be sterile and can harbor microorganisms, such as bacteria and the amoeba Acanthamoeba. While these microbes are harmless when swallowed, they can be dangerous when introduced directly to the eye surface.
These microscopic organisms can cause a rare but serious infection called Acanthamoeba keratitis, which attacks the cornea. This infection can lead to permanent vision loss if not treated aggressively. The risk is significantly higher for contact lens users, as the lens can trap the microorganism against the eye, allowing it to adhere and multiply.
Beyond the issue of sterility, bottled water is chemically different from natural human tears. Healthy tears are an isotonic solution, meaning they have a specific concentration of salts and minerals that matches the cells of the eye. Bottled water is hypotonic, containing a much lower concentration of solutes.
Rinsing with hypotonic water causes the surface cells of the cornea to absorb water through osmosis, leading to swelling, irritation, and stinging. This process disrupts the tear film, the eye’s natural protective layer, making the eye more susceptible to dryness and infection. Furthermore, the pH of still bottled drinking water is not precisely balanced for the eye’s natural environment, which can also contribute to irritation.
The Ideal Solution: Sterile Saline and Eye Wash
The safest and most effective solution for rinsing the eye is a commercially prepared sterile saline or an official eye wash solution. These products are specifically formulated to mimic the chemical properties of natural tears, making them gentle and non-irritating. Their sterile nature ensures that no harmful microorganisms are introduced to the eye during flushing.
Specialized eye rinse products are balanced for both pH and osmolarity. Their neutral pH matches the average pH of tears, which helps prevent the burning or stinging sensation that plain water can cause. Their isotonic nature matches the salt concentration of the eye’s surface, preventing the damaging osmotic movement of water into corneal cells.
Saline solution used for irrigation is essentially a 0.9% salt solution, manufactured to be sterile and non-pyrogenic. This formulation is designed to be well-tolerated by tissues, making it the preferred choice for flushing the eye and cleaning minor wounds. Keeping sterile eye wash at home or work provides the safest option for addressing routine irritations.
What to Use in an Emergency Rinsing Scenario
In a genuine emergency, such as a chemical splash or severe foreign body exposure, the priority is to flush the irritant out as quickly and completely as possible. In these situations, the risk of chemical injury or abrasion far outweighs the risk of infection from non-sterile water. Therefore, if sterile saline is not instantly available, any clean water source should be used without delay.
Clean, running tap water is often preferred over bottled water because it allows for a high volume of continuous flow, necessary to dilute and remove the irritant effectively. For chemical exposure, the eye should be flushed continuously for at least 15 minutes with lukewarm water. The goal is to keep the eyelid open and allow the stream of water to run across the eye and away from the nose.
Using tap water in an emergency bypasses the immediate sterility concern, but seeking prompt medical attention afterward remains important. The use of non-sterile water, whether bottled or tap, is a temporary measure to prevent immediate severe damage. Following the emergency flush, an eye care professional should be consulted to assess for chemical damage, corneal abrasions, or subsequent infection.