Eyedrops can sometimes cause a burning or stinging sensation upon application. While often brief and not serious, it can be uncomfortable. Understanding the factors contributing to this sensation, from the eyedrops themselves to the eye’s condition, clarifies why it occurs.
Eyedrop Composition and Properties
The chemical makeup of eyedrops plays a significant role in how they feel when applied to the eye. Differences between the drop’s properties and the eye’s natural environment can lead to irritation.
The pH level of eyedrops, if it deviates significantly from the natural pH of tears, can cause a stinging sensation. Human tears typically have a pH ranging from 6.5 to 7.6, with an average around 7.0 to 7.4. Eyedrops formulated outside this range may induce discomfort because the eye attempts to neutralize the pH difference. Some medicinal eyedrops might have a more acidic or alkaline pH for drug stability or solubility, which can contribute to the burning feeling.
Many multi-dose eyedrops contain preservatives to prevent microbial growth and extend shelf life. Benzalkonium chloride (BAK) is a common preservative known to cause irritation or toxicity to the ocular surface. BAK can disrupt the tear film, damage corneal cells, and lead to inflammation. Preservative-free eyedrops are available and can be a gentler option for individuals who experience sensitivity or use drops frequently.
The osmolality, or concentration of dissolved particles, in eyedrops also affects comfort. Tears have an approximate osmolality of 300 mOsm/L. Ideally, eyedrops should be isotonic, meaning they have a similar salt concentration to natural tears, to minimize irritation. Solutions that are hypertonic (higher salt concentration) or hypotonic (lower salt concentration) compared to tears can cause the eye to sting as it works to rebalance fluid across its surface. Hypertonic tears are common in dry eye disease, and while hypotonic drops aim to restore balance, some individuals might still feel a temporary sting.
Certain active medicinal ingredients in prescription or over-the-counter eyedrops can inherently cause a stinging sensation. For instance, vasoconstrictors found in “redness relief” drops work by constricting blood vessels, and this action can sometimes lead to irritation. Other active compounds in medications for conditions like glaucoma or allergies might also trigger a temporary burning feeling.
Pre-existing Eye Conditions
The state of an individual’s eyes can significantly influence the sensation experienced when applying eyedrops. An eye that is already compromised or irritated may react more strongly to the introduction of drops.
Dry eye syndrome is a common condition where the eyes either do not produce enough tears or tears evaporate too quickly, leading to an unstable tear film. A compromised tear film and a dry, inflamed ocular surface can make the eye more sensitive to any foreign substance, including eyedrops. Even lubricating drops, designed to soothe, might sting initially if the eye’s surface is severely dry or damaged.
Eye irritation or inflammation from conditions like conjunctivitis (pink eye), blepharitis (eyelid inflammation), or allergies can also heighten sensitivity. When the eyes are already inflamed, the delicate tissues are more reactive, making the application of eyedrops feel more intense or painful.
Any damage to the delicate corneal surface, such as a corneal abrasion (a scratch on the eye’s clear outer layer), exposes a dense network of nerve endings. This exposure makes the eye extremely sensitive, and even mild eyedrops can cause significant pain or stinging. In such cases, the burning sensation is a direct result of the underlying physical injury.
Contact lens wear can contribute to eye irritation, making eyes more reactive to drops. Prolonged contact lens use or improper hygiene can lead to dryness, discomfort, or the accumulation of deposits on the lenses. These factors can make the eyes more sensitive to eyedrops.
When to Seek Medical Advice
While a temporary burning sensation from eyedrops is often harmless, certain symptoms or persistent discomfort warrant a consultation with an eye care professional. Recognizing these warning signs can help ensure timely intervention for more serious underlying issues.
If the burning sensation from eyedrops does not subside quickly or worsens after application, it is advisable to seek medical attention. This persistence could indicate an intolerance to certain ingredients in the drops or an ongoing ocular problem that requires evaluation.
Accompanying symptoms signal a need for prompt medical advice. These red flags include severe pain, significant and increasing redness, swelling around the eyes, discharge from the eye, blurred vision, or heightened sensitivity to light. Such symptoms could point to an infection, severe inflammation, or another serious eye condition.
Signs of an allergic reaction to eyedrops, such as itching, swelling around the eyes, or a rash, require immediate attention. Discontinuing the problematic drops and consulting a doctor promptly is important to manage the allergic response.
Consulting an eye care professional is also recommended if there is uncertainty about the appropriate type of eyedrop for a specific condition or if there is a suspicion of using the wrong product. A professional can provide guidance on proper product selection and usage.