The experience of eyes stinging or burning intensely when they water is a common, uncomfortable sensation often accompanying strong emotions or environmental irritation. This stinging feeling is a direct consequence of a change in the delicate chemical balance of the tear film. Understanding the normal composition of tears and how that composition changes during excessive watering explains the biological process behind this unpleasant burning sensation.
What Tears Are Made Of
Tears are not simply saltwater but a complex, three-layered fluid called the tear film, spread across the eye’s surface with every blink. The outermost layer is the lipid layer, a thin coat of oil produced by the meibomian glands along the eyelid margins. This oily barrier slows the evaporation of the underlying watery layer, keeping the eyes moist.
The middle and thickest layer is the aqueous layer, which is mostly water, salts, proteins, and antibacterial agents like lysozyme and lactoferrin. Produced by the lacrimal glands, this layer hydrates the cornea and flushes away foreign particles. Finally, the innermost mucin layer is secreted by specialized goblet cells and helps the aqueous layer spread evenly and adhere to the eye’s surface.
Why the Tear Chemistry Causes Burning
When the eye is irritated, it triggers a rush of reflex tears intended to wash the irritant away, but this massive flush disrupts the normal chemical equilibrium and causes stinging pain. The primary mechanism behind the burning is hyperosmolarity, an elevated concentration of dissolved particles, mostly salts, in the tear fluid. This high salt concentration draws water out of the sensitive cells on the surface of the cornea and conjunctiva through osmosis, leading to cell shrinkage, damage, and irritation of the corneal nerves.
The rapid production of reflex tears, while high in volume, is often deficient in the necessary lipid and mucin components. This means the aqueous layer evaporates faster and concentrates the salts even further, intensifying the burning sensation. If the irritation is due to an allergic reaction, the tears will also contain inflammatory molecules like histamine, which directly activate the eye’s pain receptors.
Common Causes of Irritation and Excessive Watering
The stinging response is typically a defensive reaction to specific external and internal triggers that overwhelm the eye’s normal tear production rate. Environmental irritants are frequent culprits, including airborne particles like dust, smoke, pollen, or chemical fumes from household cleaners or chopping onions. The eye attempts to dilute and flush these substances out with large volumes of reflex tears, which are the tears that cause the stinging.
Seasonal and perennial allergies trigger a similar response by causing the release of histamine, a compound that leads to inflammation, itching, and excessive watering. The most common underlying cause for chronic stinging, however, is often the dry eye paradox, where the eyes are chronically dry, but water excessively. In this scenario, poor-quality basal tears evaporate too quickly, signaling the brain to produce a flood of reflex tears as a defensive measure. These reflex tears lack the proper balance of oil and mucin, offering little true lubrication and quickly becoming hyperosmolar, perpetuating the cycle of stinging and watering. Physical causes, such as a tiny foreign body stuck on the eye’s surface or a minor corneal scratch, also provoke intense reflex tearing and immediate, sharp pain.
Managing the Stinging and When to See a Doctor
To find immediate relief from the stinging, the goal is to stabilize the tear film and dilute the irritating chemical concentration. Applying preservative-free artificial tears helps by temporarily lowering the tear film’s osmolarity and providing lubrication. A cool compress placed over the closed eyelids can also reduce inflammation and calm sensitive corneal nerves. Prevention involves identifying and avoiding the specific irritant, such as using protective eyewear in dusty environments or managing underlying conditions like allergies with appropriate medication. If the stinging is a symptom of the dry eye paradox, using lubricating eye drops, particularly those with a lipid component, can help stabilize the tear film and reduce the need for irritating reflex tears.
When to Seek Medical Attention
It is important to see a doctor if the stinging is accompanied by:
- Severe pain.
- A noticeable change in vision.
- Thick yellow or green discharge.
- Symptoms that do not improve after a few days of at-home care.
- Immediate medical attention is necessary for any suspected chemical splash or a foreign object that feels lodged in the eye.